You can
round numbers
when you want to estimate an answer, or when you don't need as
precise a measurement as the one you are given.
The first thing to know about
rounding decimals is that it works exactly like rounding whole
numbers. To round to the nearest tenth, you do the same thing you do
to round to the nearest ten, except that you are working with a
different digit in the number.
A
number line can help
you round decimals.
0.70 
0.71 
0.72 
0.73 
0.74 
0.75 
0.76 
0.77 
0.78 
0.79 
0.80 

0.7

0.72
is between 0.7 and 0.8. It is closer to 0.7. Round
down to 0.7. 
0.75
is halfway
between 0.7 and 0.8. Round up to
0.8. 
0.78
is between 0.7
and 0.8. It is closer to 0.8. Round up
to 0.8. 
0.8 



We always want to keep two things
in mind when we round any number. The first
is what we are rounding to. In the above example, we are rounding to
tenths, so we should end up with one digit
to the right of the decimal point, because that is the
tenths place.
Round to the nearest tenth. 
0.68 
The number 6 is in the tenth place. 
First: look to the digit to the right of the tenth place. 
0.68

Since the number
is greater than 5 round up. 
Round up: add 1 to the digit you are
rounding to. 
0.7 
So, 0.68 rounded to the nearest tenth is 0.7. 
The second
thing to keep in mind is the method we are using to round by. In the
nearest method we look at the digit to the immediate right of the digit
we will round to. For this example we will look at the hundredth digit
and if it is a five or greater (5 through 9) we
round up (add 1 to the
digit we are rounding and drop all the digit to the right). If the digit
to the right of our rounding digit is less than 5 (0 though 4) we
round
down (drop all digits to the right of the digit we are rounding).
Example 
number to be rounded to nearest tenth 
341.757

number to the right of the tenths digit 
5 
since the number is a 5 we
round up 
341.8 
So, the answer is
341.8 
What if the
number we were rounding was 341.747 instead? 

number to be rounded to nearest tenth 
341.747 
number to the right of the tenths digit 
4 
since the number is less than 5 we round down. 
341.7 
So, the answer is
341.7 



Remember:
If less than 5,
round down. If 5 or greater, round up. 

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