Lesson 2-Rounding To The Nearest 100

Objective:

At the end of this lesson, students should be able to round numbers to the nearest 100.

We can also round numbers to the nearest hundred. When rounding a number to the nearest 100, it is important to look at the digit in the tens column. If the digit in the tens column is 4 and below (1, 2, 3, 4) we round the number down. However, if the digit is 5 and above (5, 6, 7, 8, 9) then we round the number up to the nearest 100.

Example 1

Round 122, 177 and 150 to the nearest hundred

Solution

From the diagram above:

The number 122 is closer to 100 than to 200 because the 2 in the tens column is less than 5. Therefore, we round it down to 100.

The number 177 is closer to 200 than to 100 because the 7 in the tens column is more than 5. So we round it up to 200.

The number 150 is half – way. Half- way numbers are always rounded up to the next 100 which is 200 because the 5 is in the tens column. Therefore 150 to the nearest hundred will be 200.

All numbers from 101 to 149 are rounded down to 100. All numbers from 150 to 199 are rounded up to 200.

Example 2

Round the following figures        a) 382     b) 119     c) 295   d) 32   to the nearest hundred.

Solution

From the number line above:

382 is nearer to 400 than to 300

119 is nearer to 100 than to 200

295 is nearer to 300 than to 200

32 is nearer to 0 than to 100