In relation to the post about NSLU hard drive migration. Similar steps can be taken to backup NSLU completely. There are actually some steps listed on NSLU2 linux dot org web site. However, i find the steps listed here to be simplier and easier to implement.
1. Download Clonezilla live CD. Instructions and link in previous post [NSLU hard drive migration]
2. Attached your USB drive to the computer that you are going to Boot up Clonezilla.
3. Follow on screen instructions to choose language and keyboard layout
4. Select device to image option
5. Choose where you are going to save your image. You have the option of local drive, ssh server or samba server.
6. After that, follow the instruction on screen. Choose to savedisk.
7. Follow the rest of the on screen instructions. if everything is successful, you should get your image in the location where you chose to save the image file in step 5.
More resource using Google Suggest for "Backup hard disk".
Monday, December 15, 2008
Migrating NSLU to bigger capacity Harddisk
Finally, i have managed to migrate all my data from my old hard drive (320 GB) used for my NSLU (unslung) to a bigger hard drive (500GB).
The old hard drive is starting to give me problems. For the past two power down of my NSLU, the old hard drive did not start up properly. I have to leave it running for a couple of days before finally, NSLU can boot from it. Fearing for my data in it. I got an external USB raid enclosure for 2 500GB HDD. The challenge is to migrate it smoothly.
Went to google about it. But did not have a solution that meet my needs. Finally, i was introduced to Clonezilla and GParted. These 2 application made the migration a breeze!
First download the live CD for Clonezilla and GParted. Burn the iso images into 2 CD.
Boot using GParted CD. Attached your USB drive from NSLU and the New harddrive into the computer you are booting from. Check the original partition in your old hard drive.
1. Using GParted, create the SAME number of partition on the new disk as in the old disk
- In my old hard disk, i have 3 partition. (One big ext3, one ext3 of about 120MB and one linux swap partition)
- I created 3 partition in the new disk. (1 linux swap partition, one 150MB ext3 partition, the rest of 500GB goes into the 2nd ext3 partition)
2. Once the partition are created in the new hard drive successfully, Shutdown. Change CD to Clonezilla and boot using Clonezilla CD
3. Using Clonezilla CD. Follow the on screen instructions till you reach the step where you can choose "device-device"
4. Then choose partition to partition. NOTE: When given the option, DO NOT set the target partition as the same as the source partition. If you choose to set target partition to be the same as source partition, you will end up having the same partition structure in your old disk (in my case is only 320GB, the other 180GB "went missing"). Choose to grow partition to the target partition size.
5. Repeat the partition cloning for ALL the partition in your old drive you your new drive.
After you have finish everything, Just plug in your new drive into your NSLU. You will have all your setting and all your data as what you have in your old hard drive, with the new capacity of your new drive.
The old hard drive is starting to give me problems. For the past two power down of my NSLU, the old hard drive did not start up properly. I have to leave it running for a couple of days before finally, NSLU can boot from it. Fearing for my data in it. I got an external USB raid enclosure for 2 500GB HDD. The challenge is to migrate it smoothly.
Went to google about it. But did not have a solution that meet my needs. Finally, i was introduced to Clonezilla and GParted. These 2 application made the migration a breeze!
First download the live CD for Clonezilla and GParted. Burn the iso images into 2 CD.
Boot using GParted CD. Attached your USB drive from NSLU and the New harddrive into the computer you are booting from. Check the original partition in your old hard drive.
1. Using GParted, create the SAME number of partition on the new disk as in the old disk
- In my old hard disk, i have 3 partition. (One big ext3, one ext3 of about 120MB and one linux swap partition)
- I created 3 partition in the new disk. (1 linux swap partition, one 150MB ext3 partition, the rest of 500GB goes into the 2nd ext3 partition)
2. Once the partition are created in the new hard drive successfully, Shutdown. Change CD to Clonezilla and boot using Clonezilla CD
3. Using Clonezilla CD. Follow the on screen instructions till you reach the step where you can choose "device-device"
4. Then choose partition to partition. NOTE: When given the option, DO NOT set the target partition as the same as the source partition. If you choose to set target partition to be the same as source partition, you will end up having the same partition structure in your old disk (in my case is only 320GB, the other 180GB "went missing"). Choose to grow partition to the target partition size.
5. Repeat the partition cloning for ALL the partition in your old drive you your new drive.
After you have finish everything, Just plug in your new drive into your NSLU. You will have all your setting and all your data as what you have in your old hard drive, with the new capacity of your new drive.
Friday, December 12, 2008
Your iPod needs to be reformatted for use with Windows.
Got a big shock of my life when i connected my ipod (nano 3rd generation) to my PC today.
I saw the message
"Your iPod needs to be reformatted for use with Windows. Would you like to run iTunes to restore your iPod now?
It was working well before, i did not plug it into any other computer.
No knowing if my data and stuff will still be there, i clicked "Cancel".
Went online to look for a solution. I Googled for it and found there are some support site from apple that refer to it http://support.apple.com/kb/TS1441?viewlocale=en_US but from my understanding, it is describing the steps to follow through instead of how to resolve it.
I went to a few other websites. And follow instructions here and there. Finally, after i plug in my ipod, the message is no more there. Normal operation resumes.
Here are the steps i took;
1. Switch ipod to hold.
2. Swith ipod to UN-hold
3. Press "MENU" and centre button together. Hold down both buttons until the ipod reset itself.
4. After reset, "Off" the ipod by pressing and holding the "play / pause" button
5. "On" the ipod again
After the above steps, i tried to plug into my computer again. And it works! =D
More resource using Google Suggest for "ipod help"
I saw the message
"Your iPod needs to be reformatted for use with Windows. Would you like to run iTunes to restore your iPod now?
It was working well before, i did not plug it into any other computer.
No knowing if my data and stuff will still be there, i clicked "Cancel".
Went online to look for a solution. I Googled for it and found there are some support site from apple that refer to it http://support.apple.com/kb/TS1441?viewlocale=en_US but from my understanding, it is describing the steps to follow through instead of how to resolve it.
I went to a few other websites. And follow instructions here and there. Finally, after i plug in my ipod, the message is no more there. Normal operation resumes.
Here are the steps i took;
1. Switch ipod to hold.
2. Swith ipod to UN-hold
3. Press "MENU" and centre button together. Hold down both buttons until the ipod reset itself.
4. After reset, "Off" the ipod by pressing and holding the "play / pause" button
5. "On" the ipod again
After the above steps, i tried to plug into my computer again. And it works! =D
More resource using Google Suggest for "ipod help"
Monday, October 13, 2008
CPF Housing Loan Early Repayment?
You will be redirected to the download link immediately after payment.
Wednesday, August 27, 2008
Java applet problem in Firefox 3
Arggzz.... updated to Firefox 3 automatically yesterday.
Today, tried to access some sites with Java applet and Firefox 3 is not working well!
Mostly, internet banking sites.
Without tweaking,
DBS internet banking is working
OCBC internet banking is working.
UOB internet banking cannot initialize the java applet.
Same goes for Fundsupermart.
And i read in some forum that Citibank internet banking is not working well with Firefox 3 too.
Went to google for the solution and realized that there is 2 ways to resolve this.
1. Download User Agent Switcher add on for Firefox
******* from Mozilla forum ***************
I had the same problem with FF3. Called the citibank support. Was given a solution that works for now.
1. Download this addon (User Agent Switcher) from the URL
https://addons.mozilla.org/en-US/firefox/addon/59
2. Install it and on the FF3 Tools ---> User Agent Switcher, and select either one of the browser. Then login. Should work.
3. You'll also have to perform step 2 everytime you want to use FF3 to logon to Citibank.
4. I think the problem is not exactly with the applet but rather the new FF3 (aka Mozilla 5) is not yet recognised by their system. They are using BEA so this could be a security feature to ensure only the recognised (or compatible) browser types get connected. Hope they can get the changes done quickly to rectify this.
******* from Mozilla forum ***************
OR
Another contributor at the forum suggested the following:
******* from Mozilla forum ***************
1. type "about:config" in the url.
2. right click and select NEW --> STRING
3. type in "general.appname.override" as preference name.
4. type in any word such as "hello" as value.
voila! citibank singapore should load correctly now. the reason i think is that the website couldnt work correctly with some versions of Netscape, so citibank purposely blocked those browsers from loading. and strangely, firefox still uses Netscape as its browser 'appname' identifier. alternatively, you can use the useragent switched addon, but you will have to click on it to load a different useragent profile everything you wanna do the online banking.
******* from Mozilla forum ***************
In the end, i used the second option, Added "general.appname.override" BUT with an empty value. And it works for me!
I hope Firefox can have an update soon for this issue.
Today, tried to access some sites with Java applet and Firefox 3 is not working well!
Mostly, internet banking sites.
Without tweaking,
DBS internet banking is working
OCBC internet banking is working.
UOB internet banking cannot initialize the java applet.
Same goes for Fundsupermart.
And i read in some forum that Citibank internet banking is not working well with Firefox 3 too.
Went to google for the solution and realized that there is 2 ways to resolve this.
1. Download User Agent Switcher add on for Firefox
******* from Mozilla forum ***************
I had the same problem with FF3. Called the citibank support. Was given a solution that works for now.
1. Download this addon (User Agent Switcher) from the URL
https://addons.mozilla.org/en-US/firefox/addon/59
2. Install it and on the FF3 Tools ---> User Agent Switcher, and select either one of the browser. Then login. Should work.
3. You'll also have to perform step 2 everytime you want to use FF3 to logon to Citibank.
4. I think the problem is not exactly with the applet but rather the new FF3 (aka Mozilla 5) is not yet recognised by their system. They are using BEA so this could be a security feature to ensure only the recognised (or compatible) browser types get connected. Hope they can get the changes done quickly to rectify this.
******* from Mozilla forum ***************
OR
Another contributor at the forum suggested the following:
******* from Mozilla forum ***************
1. type "about:config" in the url.
2. right click and select NEW --> STRING
3. type in "general.appname.override" as preference name.
4. type in any word such as "hello" as value.
voila! citibank singapore should load correctly now. the reason i think is that the website couldnt work correctly with some versions of Netscape, so citibank purposely blocked those browsers from loading. and strangely, firefox still uses Netscape as its browser 'appname' identifier. alternatively, you can use the useragent switched addon, but you will have to click on it to load a different useragent profile everything you wanna do the online banking.
******* from Mozilla forum ***************
In the end, i used the second option, Added "general.appname.override" BUT with an empty value. And it works for me!
I hope Firefox can have an update soon for this issue.
Thursday, August 21, 2008
Roger Crawford-Short Motivational Clip
Roger Crawford was born with four underdeveloped limbs--basically, from his elbows down and from his knees down, his limbs did not grow properly. He have two fingers on his right hand and one on his left. As a result, doctors predicted he would be unable to walk and would have limited dexterity.
Check out America's Possibility Coach, Roger Crawford and be amazed at human's ability to overcome.....
"Challenges are inevitable. But Defeat is optional" ~ Roger Crawford.
Check out America's Possibility Coach, Roger Crawford and be amazed at human's ability to overcome.....
"Challenges are inevitable. But Defeat is optional" ~ Roger Crawford.
Thursday, July 31, 2008
One or more files could not be updated - Thunderbird and Firefox in Windows Vista
I have the problem of thunderbird software update failed. Every time i start thunderbird, i will get the error message pop up "One or more files could not be updated. Please make sure all other applications are closed and that you have permission to modify files, and then restart Thunderbird to try again"
After putting up with it for a couple of day, i finally had enough...
Went to google for a solution. Came across this blog that recommended deleting some files in the profile's update directory. However, i am worried that that might caused some other problem. Apparently, the issue caused is because when the application is not running in administrator mode in Vista computer, it do not have privileges to do lots of things.
So the simple solution is to close Thunderbird and use "Run as administrator" to start it up.
After that, it updates successfully and the irritating message is gone!
After putting up with it for a couple of day, i finally had enough...
Went to google for a solution. Came across this blog that recommended deleting some files in the profile's update directory. However, i am worried that that might caused some other problem. Apparently, the issue caused is because when the application is not running in administrator mode in Vista computer, it do not have privileges to do lots of things.
So the simple solution is to close Thunderbird and use "Run as administrator" to start it up.
After that, it updates successfully and the irritating message is gone!
Saturday, July 19, 2008
Building Rapport With People
I have been reading personal development and self help book for sometime. Recently started to attend seminars. This weekend, i am attending Blair Singer's 2 day sales and leadership seminar.
In the seminar, when talking about building rapport with people we are working with. It boils down to this few key points
1. Be interested. Be genuinely interested in what your counter part is saying.
2. Enter into their world 1st. Ask them about themselves, what do they do, what are their interest.
3. From there, find common ground (shared realities). Build on those shared realities.
4. Ask for verification. Check with our partners if our understanding of the topics in the conversations are correct.
From the interactions establish above. Take note of what type of person our partners are primarily. Visual, Auditory or Kinesthetic. Each type exhibits some main characteristics which i will talk about later.... Now i need to go back to the seminar... lunch time over! =D
In the seminar, when talking about building rapport with people we are working with. It boils down to this few key points
1. Be interested. Be genuinely interested in what your counter part is saying.
2. Enter into their world 1st. Ask them about themselves, what do they do, what are their interest.
3. From there, find common ground (shared realities). Build on those shared realities.
4. Ask for verification. Check with our partners if our understanding of the topics in the conversations are correct.
From the interactions establish above. Take note of what type of person our partners are primarily. Visual, Auditory or Kinesthetic. Each type exhibits some main characteristics which i will talk about later.... Now i need to go back to the seminar... lunch time over! =D
Thursday, May 1, 2008
Migrating putty - porting to new pc
Putty is a client end program for SSH, telnet and RLogin network protocol.
I use it frequently in my line of work. The only issue i have with it is that i cannot find any configuration file for it that i can migrate and port over to a new pc. Over the past few years, i have changed my computer several time and each time i would need to reconfigure putty again. Although it is quite easy to set up, if there is a convenient way to migrate and port my configuration over, i would want to do that.
Searches on Google reveals that putty stores the configurations in window's registry. In order to port the configurations, we will need to export the correct branch from the registry. Steps below illustrate how to migrate putty setting to new computer.
1. Open regedit (press win key + r and type regedit in the run window)
2. Look for simon (press ctrl + F)
3. Goto File menu, click export and save the registry record as putty registry.
4. Copy the exported registry file to a usb thumb drive and copy it to the new computer.
5. Right click on the registry file in the new computer, choose merge.
I use it frequently in my line of work. The only issue i have with it is that i cannot find any configuration file for it that i can migrate and port over to a new pc. Over the past few years, i have changed my computer several time and each time i would need to reconfigure putty again. Although it is quite easy to set up, if there is a convenient way to migrate and port my configuration over, i would want to do that.
Searches on Google reveals that putty stores the configurations in window's registry. In order to port the configurations, we will need to export the correct branch from the registry. Steps below illustrate how to migrate putty setting to new computer.
1. Open regedit (press win key + r and type regedit in the run window)
2. Look for simon (press ctrl + F)
3. Goto File menu, click export and save the registry record as putty registry.
4. Copy the exported registry file to a usb thumb drive and copy it to the new computer.
5. Right click on the registry file in the new computer, choose merge.
Sunday, March 30, 2008
Paulo Coelho ~ Traveling Differently
Recently, i was on a Singapore Airline flight to Ho Chi Minh City. On the flight, came across this interesting article about traveling by Paulo Coelho, best selling author of The Alchemist. The ideas that Paulo Coelho brought across in the article is unique and very logical. Here is a summary of the article.
Why do we travel? What do we want to get out from our traveling? Most of the time, we would want to learn more about the people, the place and the culture. The journey itself is a way to learn.
Very interestingly, Paulo Coelho advocate NOT visiting the museum! It is because, visiting museum requires lots of time and objectivity. And often we see a lot in the museum but cannot remember much! Very true isn't it?
Instead of the museum, go to the local bar. Find places where the locals hang out for a drink and chat over the most mundane stuff in life. This is where the live of the city can be found. Sit down, relax, enjoy a drink and observer the people coming in and out of the place. Quoting from the article "one cannot judge the beauty of a path merely by looking at its entrance." Do not judge, be there to learn and feel the spirit of the ambiance.
Be willing to meet more people, especially the local. Be open and forward. Talk to someone on the streets, ask for directions. If they are not able to help you with it, ask someone else. Try, try and try again. The chances are we will find excellent company.
Do not travel with tour groups! Tour groups are a disguised way of pretending to be overseas! You are still with a group of people who share similar culture and background. You are still speaking the same language. Most of the time, the focus is not on the places that you are visiting. I guess, if you have the experience of traveling along and traveling in a tour group, you will get what Paulo Coelho is trying to say.
Do not judge. Take things as they are. We just need to acknowledge the things that are happening around us. Do not compare price, do not compare environment, do not compare the quality of life. We are there to learn how they live, what they can teach us and learn their point of view. What is their reality? What is extraordinary to them? Very true isn't? Some of the very simple things that we take for granted like clean water from tap may be an extraordinary thing to them. Some of the things that are extraordinary to us, like long necks with rings and big lips with discs are actually normal and beautiful!
We should travel with a mindset "know that everyone understand you". I am kind of puzzle when i read this line. Upon reading more, i get more clarity from it. There are many forms of communications and verbal communications just makes up a percentage of it. Even if we do not know the language, be courageous. In the event that we got lost, all we need is a hotel card, hop onto a taxi and show the card to the driver.
Don't buy much. Spend money in a way that we do not need to carry. Go to the theatre, restaurants and just take a walk around. Best of all, there will be no need to pay for any excess baggage!
Take your time travel a place. It is better to visit one place for five days than five places for a week. There is this interesting line that i would like to quote from the article:
"A city is like a capricious woman who needs time to be seduced and reveal herself completely"
Lastly, the journey itself is an adventure. It is more important to discover church that no one heard of, than visiting an attraction of thousands of chatting tourist! Yes, you may like to visit attractions to see how they are like. It is also equally important to get lost in the streets, wonder around. We will never know what we will find!
I will end with this quote
"Feel free to look for something, without knowing what it is" ~ Paulo Coelho.
Check out the full article at
Travelling Differently at Walking the Path - The Pilgrimage
Why do we travel? What do we want to get out from our traveling? Most of the time, we would want to learn more about the people, the place and the culture. The journey itself is a way to learn.
Very interestingly, Paulo Coelho advocate NOT visiting the museum! It is because, visiting museum requires lots of time and objectivity. And often we see a lot in the museum but cannot remember much! Very true isn't it?
Instead of the museum, go to the local bar. Find places where the locals hang out for a drink and chat over the most mundane stuff in life. This is where the live of the city can be found. Sit down, relax, enjoy a drink and observer the people coming in and out of the place. Quoting from the article "one cannot judge the beauty of a path merely by looking at its entrance." Do not judge, be there to learn and feel the spirit of the ambiance.
Be willing to meet more people, especially the local. Be open and forward. Talk to someone on the streets, ask for directions. If they are not able to help you with it, ask someone else. Try, try and try again. The chances are we will find excellent company.
Do not travel with tour groups! Tour groups are a disguised way of pretending to be overseas! You are still with a group of people who share similar culture and background. You are still speaking the same language. Most of the time, the focus is not on the places that you are visiting. I guess, if you have the experience of traveling along and traveling in a tour group, you will get what Paulo Coelho is trying to say.
Do not judge. Take things as they are. We just need to acknowledge the things that are happening around us. Do not compare price, do not compare environment, do not compare the quality of life. We are there to learn how they live, what they can teach us and learn their point of view. What is their reality? What is extraordinary to them? Very true isn't? Some of the very simple things that we take for granted like clean water from tap may be an extraordinary thing to them. Some of the things that are extraordinary to us, like long necks with rings and big lips with discs are actually normal and beautiful!
We should travel with a mindset "know that everyone understand you". I am kind of puzzle when i read this line. Upon reading more, i get more clarity from it. There are many forms of communications and verbal communications just makes up a percentage of it. Even if we do not know the language, be courageous. In the event that we got lost, all we need is a hotel card, hop onto a taxi and show the card to the driver.
Don't buy much. Spend money in a way that we do not need to carry. Go to the theatre, restaurants and just take a walk around. Best of all, there will be no need to pay for any excess baggage!
Take your time travel a place. It is better to visit one place for five days than five places for a week. There is this interesting line that i would like to quote from the article:
"A city is like a capricious woman who needs time to be seduced and reveal herself completely"
Lastly, the journey itself is an adventure. It is more important to discover church that no one heard of, than visiting an attraction of thousands of chatting tourist! Yes, you may like to visit attractions to see how they are like. It is also equally important to get lost in the streets, wonder around. We will never know what we will find!
I will end with this quote
"Feel free to look for something, without knowing what it is" ~ Paulo Coelho.
Check out the full article at
Travelling Differently at Walking the Path - The Pilgrimage
Thursday, March 6, 2008
Easy Simple Mental Addition and Subtraction
Mental calculations can be quite daunting. However, do you know that we can easily do mental calculation for addition and subtraction up 4 digits.
The theory goes like this:
1) Human mind can hold up to 7 bits of information consciously at any one time. (why do you thing most phone numbers are 7 or 8 digits? =D)
2) It is easier to do the addition or subtraction from left to right (most significant digit first).
3) Use some common sense to do some simplification to the questions.
Now for the exciting part:
Lets say we are going to do addition for 56 + 43. Instead of the conventional way of doing from right to left (least significant digit first)
We do addition from the most significant digit
56 + 43 = 56 + 40 + 3
=> 56 + 40 = 96 then 96 + 3 = 99
It may seems trivial at this stage to do mental addition subtraction from left to right. It becomes more apparent as we do number with more digits.
For subtraction:
95 - 48
There is 2 ways. First is the same as above, doing from left to right (the most significant digit first)
95 - 40 = 55 then 55 - 8 = 47
Second, since 48 is close to 50, we can do this:
95 - (50 - 2) = 95 - 50 + 2
95 - 50 = 45 then 45 + 2 = 47.
Now lets take a look at addition and subtraction for the hundred position.
567 + 325
=> 567 + 300 + 20 + 5
=> 867 + 20 + 5
=> 887 + 5
=> 892
786 + 593
=> 786 + 500 + 90 + 3
=> 1286 + 90 + 3
=> 1376 + 3
=> 1379
Try out these sums mentally. You will realized that with practice, doing addition and subtraction mentally is really easier when we do it from left to right (from the most significant digit)
687 - 396
=> 687 - 300 - 90 -6
=> 387 - 90 - 6
=> 297 - 6
=> 291
You will realized that when we need to carry over for subtraction, it is gets a bit more sticky.
And easier approach will be as follows:
Since 396 is close to 400, we can do this:
687 - (400 - 4)
=> 687 - 400 + 4
=> 287 + 4
=> 291
It takes more practice as the number of digits increase, as human's conscious mind can hold up to 7 bits of information, we can easily to up to 4 digit and 3 digit addition and subtraction.
After a bit of practice on this technique, we can easily do mental addition and subtraction without the hassle of using a calculator for anything less than a thousand.
The theory goes like this:
1) Human mind can hold up to 7 bits of information consciously at any one time. (why do you thing most phone numbers are 7 or 8 digits? =D)
2) It is easier to do the addition or subtraction from left to right (most significant digit first).
3) Use some common sense to do some simplification to the questions.
Now for the exciting part:
Lets say we are going to do addition for 56 + 43. Instead of the conventional way of doing from right to left (least significant digit first)
We do addition from the most significant digit
56 + 43 = 56 + 40 + 3
=> 56 + 40 = 96 then 96 + 3 = 99
It may seems trivial at this stage to do mental addition subtraction from left to right. It becomes more apparent as we do number with more digits.
For subtraction:
95 - 48
There is 2 ways. First is the same as above, doing from left to right (the most significant digit first)
95 - 40 = 55 then 55 - 8 = 47
Second, since 48 is close to 50, we can do this:
95 - (50 - 2) = 95 - 50 + 2
95 - 50 = 45 then 45 + 2 = 47.
Now lets take a look at addition and subtraction for the hundred position.
567 + 325
=> 567 + 300 + 20 + 5
=> 867 + 20 + 5
=> 887 + 5
=> 892
786 + 593
=> 786 + 500 + 90 + 3
=> 1286 + 90 + 3
=> 1376 + 3
=> 1379
Try out these sums mentally. You will realized that with practice, doing addition and subtraction mentally is really easier when we do it from left to right (from the most significant digit)
687 - 396
=> 687 - 300 - 90 -6
=> 387 - 90 - 6
=> 297 - 6
=> 291
You will realized that when we need to carry over for subtraction, it is gets a bit more sticky.
And easier approach will be as follows:
Since 396 is close to 400, we can do this:
687 - (400 - 4)
=> 687 - 400 + 4
=> 287 + 4
=> 291
It takes more practice as the number of digits increase, as human's conscious mind can hold up to 7 bits of information, we can easily to up to 4 digit and 3 digit addition and subtraction.
After a bit of practice on this technique, we can easily do mental addition and subtraction without the hassle of using a calculator for anything less than a thousand.
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