ABE Math Tutorials/Whole numbers/Long addition and subtraction
Long addition and subtraction
Whole numbers 
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Adding and Subtracting Larger Numbers
Adding 4 and 3 is simple, right? We can write it down like this:
We simply line up the 4 and the 3, then add; then put the answer underneath.
Adding numbers with single digits is easy  we do it in our heads! But adding numbers with more than one digit (numbers like 34, 112, 303) takes more work. The first thing we must do is to make sure that the digits in the ones' place (remember "place value"?) are all lined up; the digits in the tens' place are all lined up; and so on with the hundreds', the thousands', etc. It's easier if we can see an example:
What happens when we try to add numbers with larger digits,like 59 + 85?
Now we have 3 digits to add in the tens' place: 1 + 5 + 8 = 14. Once again, we can only put one digit in the tens' space below, so we put down the "4" and carry the "1" over into the hundreds' place. Now we add the hundreds' (there is only one of them) to get the final answer: 144.
All addition is done the same way. First, line up your numbers so each digit is in its proper column. Then, add up all the digits in the ones' place; write down the total ones' digit and carry the tens (if there are any) over into the tens' column. Then add up all the tens' digits, write down the total digit and carry (if necessary) over into the hundreds' column; add up all the hundreds' digits  and so on. {{Activity }} Ready to try a few examples? Add the following groups of numbers
 454 + 282 =
 5937 + 408 =
 101 + 9999 =
See answer below