You can round
numbers to tell about
how much or about how
many.
A
number line can help you to round numbers.
258 is closer to 300
than 200.
To
round numbers:
Find the place you
are rounding to.
Look at the digit
to its right.
If
the digit to the right of the place one is rounding to is
less
than 5, round down
;
if it is 5 or greater, round up .
Example 1: Round to the nearest ten:
25, 52, 78
25
5
=
5
round
up.
25 =
30
52
2<
5
round down.
52 =
50
78
8> 5
round up.
78 = 80
Example 2:
20
21
22
23
24
25
26
27
28
29
30
20
22
is between 20 and 30. It is closer to
20.
Round
down to 20.
25
is halfway
between 20 and 30.
Round up to 30.
28
is between 20 and
30. It is closer to 30. Round up
to 30.
30
Example 3:
You can use a ruler to measure an object to the nearest
centimeter.
The pencil
measures halfway between 12 and 13 centimeters, or 12.5
centimeters.
Follow the rules for rounding.
12.5 = 5
round
up.
12.5 = 13 centimeters.
You can use a number
line to check your answer.
12.5
is halfway
between 12 and 13 so you round up.
12.5 = 13
;
.
25
5
=
5
round
up.
52
2<
5 
78
8> 5 
