Rounding
is one way to estimate
sums and difference.
Round 53,
55, and 58 to
the nearest ten. Estimate the sum.
50 
51 
52 
53 
54 
55 
56 
57 
58 
59 
60 


50

53
is between 50 and 60. It is closer to 50 Round
down to 50. 
55
is halfway
between 50 and 60. Round up to
60. 
58
is between 50 and
60. It is closer to 60. Round up
to 60. 
60 


53
50
55
60
+58
+ 60
?
170 



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: Round
to the nearest ten.
Estimate
the sum. 
Estimate
the difference. 
36
+44
?

40
+40
80

52
25
?

50
30
20


Example: Round to the nearest hundred.
Estimate
the sum. 
Estimate
the difference. 
256
+444
?

300
+400
700

536
154
?

500
200
300



Remember to round
both numbers to the same place value when estimating a sum
or a difference. When a number is
halfway between two numbers, round
to the greater number. 
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