Idiot\'s Guides Basic Math and Pre-Algebra

Chapter 2: Arithmetic 17

Adding Longer Columns

Addition is officially a binary operation. That means that it works with two numbers at a time.

In fact, all four arithmetic operations (addition, subtraction, multiplication, and division) are

binary operations, but for addition (and multiplication) it is possible to chain a series of operations

together. When you add 4 + 9 + 7 + 5, you’re actually only adding two numbers at a time.

You add 4 + 9 to get 13, then that 13 + 7 to get 20, and then 20 + 5 to get 25. The same kind

of chaining works with larger numbers, as long as you remember to stack the numbers so that

decimal points, and therefore place values, are lined up.

Suppose you wanted to add 59,201 + 18,492 + 81,002 + 6,478. First, stack them with the (invisible)

decimal points aligned.

Add each column, regrouping and carrying over to the next place if you need to. Chain the

addition in each column. In the ones column, you’re adding 1 + 2 + 2 + 8, so 1 + 2 is 3, 3 + 2 is

5, and 5 + 8 is 13. Put the 3 in the ones column of the answer and carry the 1 ten to the tens

column.

Add the tens column. 0 + 9 + 0 + 7 + the 1 you carried is 17, so put down the 7 and carry the 1.



59,201

18,492

81,002

6,478



59,201

18,492

81,002

6,478

3

1



59,201

18,492

81,002

6,478

73

11