Rounding whole numbers is a form of estimation that involves finding an answer close to the exact value. When rounding to the nearest ten, numbers ending in 5-9 round up, while numbers ending in 1-4 round down. Similarly, when rounding to the nearest hundred, numbers ending in 00-49 round down and 50-99 round up. Examples are provided to illustrate rounding 83 to the nearest ten (80) and 423 to the nearest hundred (400).

1. ROUNDING WHOLE
NUMBERS

2. ESTIMATION
• It is the process of finding an answer
that is close to the exact answer.

3. Observe that whole numbers 11,12, 13 and 14
are nearer to 10, so you round them down to
10.
Whole numbers 16,17,18 and 19 are nearer to
20, so you round them up to 20.
The number 15 is halfway between 10 and 20.
The rule is to round up numbers ending in 5.

4. When rounding a number to the nearest ten, look at the
ones or units digit.
If the ones digit is 5, 6,7, 8 and 9, round up to the nearest
ten.
If the ones digit is 1, 2, 3, and 4, round down to the
nearest ten.
EXAMPLE:
Round off 83 to the nearest ten.
The answer is 80.

5. When rounding a number to the nearest hundred, look at
the last two digits.
If the last two digits are from 00 to 49, round down to the
nearest hundred.
If the last two digits are from 50 to 99 round up to the
nearest hundred.
EXAMPLE:
Round off 423 to the nearest hundred.
The answer is 400.