The first thing you should do when solving an addition problem is to make sure you set up the problem correctly. All this means is making sure all your numbers are lined up correctly. Your ones digits are all in a row, your tens digits are all in a row etc.
For example, let’s say your asked to add
24 + 5,679 + 367
Although all three numbers have different numbers of digits, when you set up the problem all numbers should be lined up farthest as possible to the right. It doesn’t matter what order the numbers are in, but I like to put larger numbers on the top.
When you start solving, start in the ones column (the rightmost column). Start from the top and go down. So 9 + 7 + 4. If you can use a calculator on this section of the test to be sure, or you can just do it in your head. Nine plus seven is sixteen, and sixteen plus four is twenty. Twenty (20) is two digits, however, and since your only working in one column, what should you do? The answer is carry over. You carry over the tens digit (in this case the 2) to the next column, and leave the ones digit (in this case the 0) in the ones digit of the answer.
Now you start on the second column. Don’t forget to include the 2 you carried over from the last step.
2 + 7 + 6 + 2 = 17
17 is two digits, so you need to carry over again. This time you carry over the 1 and leave the 7 in the answer.
Now 1 + 6 + 3 = 10. You need to carry over the one.
The result of adding numbers together is called the sum. So 6,070 is the sum of 5,679, 367 and 24.