Reteaching
Name
Estimating Sums and
Differences of Mixed Numbers
10-1
You can use rounding to estimate sums and differences of
fractions and mixed numbers.
How to round fractions:
If the fractional part is greater than or equal to _​ 12 ​, round up to the
next whole number.
Example: Round 3​ _57 ​to the nearest whole number.
​ _57 ​is greater than _​ 12 ​, so 3​ _57 ​rounds up to 4.
If the fractional part is less than _​ 12 ​, drop the fraction and use the
whole number you already have.
Example: Round 6​ _13 ​to the nearest whole number.
​ _13 ​is less than _​ 12 ​, so drop _​ 13 ​and round down to 6.
How to estimate sums and differences of fractions and mixed
numbers:
Round both numbers to the nearest whole number. Then add or
subtract.
Example: Estimate 4​ _18 ​1 7​ _23 ​.
4​ _18 ​rounds down to 4.
7​ _23 ​rounds up to 8.
4 1 8 5 12
So, 4​ _18 ​1 7​ _23 ​is about 12.
Round to the nearest whole number.
1. 8​ _56 ​
2. 13​ _89 ​
3. 43​ _13 ​
40 ​ 
4. 7​ __
81
5. 29​ _45 ​
6. 88​ _24 ​
3  ​ 
7. 19​ __
34
41 ​ 
8. 63​ __
49
Estimate each sum or difference.
9. 7​ _19 ​1 8​ _25 ​
7  ​ 
10. 14​ _58 ​2 3​ __
10
11. 2​ _14 ​1 5​ _12 ​1 10​ _34 ​
1  ​ 
12. 11​ _35 ​2 4​ __
12
11 ​ 1 5​ _
1 ​
13. 9 1 3​ __
14
9
2  ​ 
14. 15​ _67 ​2 12​ __
10
R 10•1
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Practice
Name
10-1
Estimating Sums and
Differences of Mixed Numbers
Round to the nearest whole number.
1. 3​ _38 ​
5  ​ 
2. 6​ __
11
11 ​ 
3. 1​ __
20
6  ​ 
4. 12​ __
13
Estimate each sum or difference.
5. 3​ _14 ​+ 2​ _56 ​
6. 5​ _69 ​− 1​ _34 ​
5  ​ + 8​ _
3 ​
7. 5​ __
5
13
8. 11 − 6​ _37 ​+ 2​ _25 ​
Robert and May are competing in a
track meet. The table at the right
shows the results of their events.
Participant
9. Robert says his better jump was
about 1 ft longer than May’s better
jump. Is he correct?
Event
Results/Distance
Long jump
Robert
62​ _51 ​ft
Softball throw
Long jump
May
5
2
1. 6​ __
  ​ ft 2. 5​ _ ​ ft
12
3
1. 4​_ 23 ​ft 2. 4​ _43 ​ft
Softball throw
71​ _87 ​ft
10. Use the table above. If the school record for the softball throw is
78 ft, about how much farther must Robert throw the ball to match
the record?
A 15 ft
B 16 ft
C 18 ft
D 20 ft
11. Consider the sum of _​ 35 ​+ _​ 34 ​. Round each fraction and estimate
the sum. Add the two fractions using a common denominator
and then round the result. Which estimate is closer to the
actual answer?
P 10•1
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