WHOLE NUMBERS – ROUNDING WITH ADDITION

There are two steps to solving these problems. First, round the numbers. Then add.

Concept for Rounding: Use rounding to make difficult calculations easier to perform, especially when you do not need exact numbers in your calculations.

Steps for Rounding

Step 1 | Find the digit you want to round to. Call it the target digit.
Step 2 | Look at the digit to the right of the target digit.
Step 3 | If the digit to the right of the target digit is 5 or more, add 1 to the target digit. If the digit to the right of the target digit is less than 5, do not change the target digit.
Step 4 | In either case, change all digits to the right of the target digit to zeros.

Example of Rounding Round 31,338,180 to the nearest hundred

Step 1 | Find the digit you want to round to. Call it the target digit. In this case we are targeting the hundreds digit which is a 1 in 31,338,180. | 31,338,1 80
Step 2 | Look at the digit to the right of the target digit. That digit is an 8. | 31,338,1 8 0
Step 3 | If the digit to the right of the target digit is a 5 or more, add 1 to the target digit. 8 is more than 5, so we will add 1 to the target digit. Our target digit is now a 2. (If the digit to the right of the target digit had been less than a 5, we would not have changed the target digit.) | 31,338,2 8 0
Step 4 | In either case, change all digits to the right of the target digit to zeros. 31,338,180 rounded to the nearest hundred is 31,338,200. | 31,338,2 00

Concept for Addition: Use addition to combine quantities, or find a total, or a sum. The answer to an addition equation is called the sum. Follow these steps to add whole numbers.

Steps for Addition

Step 1 | Arrange the numbers being added so digits with the same place value are aligned.
Step 2 | Start with the ones column. Add the numbers in the ones column, placing the result underneath the line in the ones column. When a column of digits has a sum greater than 9, carry to the next column on the left.
Step 3 | Working from right to left, add the numbers in each column.

Example of Addition Add 169 and 683

Step 1 | Arrange the numbers being added so digits with the same place value are aligned. | 1 6 9 +6 8 3
Step 2 | Start with the ones column. Add the numbers in the ones column. (9 + 3 = 1 2). Note that the sum of the digits in the ones column, 1 2, is greater than 9. When a column of digits has a sum greater than 9, carry to the next column on the left. Therefore, write 2 at the bottom of the ones column, and carry 1 to the top of the tens column. | 1 1 6 9 +6 8 3 2
Step 3 | Working from right to left, add the numbers in each column. 1 + 6 + 8 = 1 5 (When a column of digits has a sum greater than 9, carry to the next column on the left.) | 1 1 1 6 9 +6 8 3 52
Step 3 | Continue adding the remaining columns, carrying when necessary. 1 + 1 + 6 = 8 | 1 1 1 6 9 +6 8 3 852
Step 3 | The sum of 1 6 9 and 6 8 3 is 852 | 1 1 1 6 9 +6 8 3 852