Warm Up

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Warm Up
Problem of the Day
Lesson Presentation
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Warm Up Divide. Write each answer in simplest
form.
3 10
1. 4
3 4
6 5

2.
2 3
5 6
3.

15
3
Problem of the Day Fill in the square using the
numbers 513 so that all sums (rows, columns, and
main diagonals) are the same.
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Learn to estimate sums and differences of
fractions and mixed numbers.
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Sometimes, when solving problems, you may not
need an exact answer. To estimate sums and
differences of fractions and mixed numbers,
round each fraction to 0, , or 1. you can use a
number line to help.
1 2
6
You can also round fractions by
comparing numerators with denominators.
1 2
Round to 1 if the numerator is nearly equal to
the denominator.
Round to 0 if the numerator is much smaller
than the denominator.
Round to
if the
numerator is about half the denominator.
Examples
Examples
Examples
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Insert Lesson Title Here
Additional Example 1 Measurement Application
3 5
A blue whale can grow to 33 m long, while
1 2
the great white shark may be as long as 4 m.
About how much longer is the blue whale?
Round each mixed number.



Subtract.
The blue whale is about 29 m longer.
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Insert Lesson Title Here
Try This Example 1
A Cocker Spaniel may grow to weigh about 11
kilograms while the Chihuahua will not weigh more
than 2 kilograms. About how much more can a
Cocker Spaniel weigh?

7 8
Round each mixed number.


3

Subtract.
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Additional Example 2A 2B Estimating Sums and
Differences
Estimate each sum or difference.
7 9
1 5
A.

1 5
7 9
0
Round each mixed fraction.
1
Subtract.
1 0 1
Round each mixed fraction.
3
Add.
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Additional Example 2C Estimating Sums and
Differences
Estimate the sum.
1 8
7 12
C.
2

1 2
Round each number.
2
Add.
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Try This Example 2A 2B
Estimate each sum or difference.
7 8
1 6
A.

1 6
7 8
0
Round each mixed fraction.
1
Subtract.
1 0 1
Round each mixed fraction.
2
Add.
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Try This Example 2C
Estimate the sum.
2 9
8 15
C.
4

1 2
Round each number.
4
Add.
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When exact answers are not needed for a problem,
you can use estimation. When exact answers are
needed, an estimate can help you decide if your
answer is reasonable.
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Additional Example 3A Deciding If an Estimate is
Enough
Decide if you need an exact answer or if an
estimate is enough.
A. Michael knows there will be 18 people at his
party. He plans to give each person a cup
serving of popcorn. If he can buy popcorn in
10-cup bags, how many bags should he buy?
2 3
1
Since he will be buying the popcorn in 10 cup
bags, an estimate of the amount will give him
enough information to decide how many bags of
popcorn to buy.
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Additional Example 3B Deciding If an Estimate is
Enough
Decide if you need an exact answer or if an
estimate is enough.
B. For a soccer celebration, Ellis buys rolls for
5.29 and 3 pounds of barbequed ham for
1 4
9 per pound. How much does she spend for the
food?
Since the problem is asking for the exact amount
of money she spends, an estimate would not be
appropriate.
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Insert Lesson Title Here
Try This Example 3A
Decide if you need an exact answer or if an
estimate is enough.
3 4
Cynthia has two dogs. Each dog is fed 1
cups of dog food each day. If she buys a 30
lb bag of dog food, is that enough to last for
three weeks?
Since she is only trying to get an idea of how
long a 30 lb bag of dog food will last, an
estimate should give her enough information to
decide .
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Insert Lesson Title Here
Try This Example 3B
Decide if you need an exact answer or if an
estimate is enough.
Williams uncle was going on a 14-day camping
trip. He is required to take 1 pills of a
certain medication each day. How many pills
should he take with him on this trip?
1 2
Since his uncle must take a certain amount of
pills each day for a medical condition, an
estimate would not be appropriate.
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Insert Lesson Title Here
Lesson Quiz
1. The new show arena being built in Franklin
County is 150 feet long and 110 feet wide.
Estimate the difference between the
length and width.
3 4
1 2
40 ft
Estimate each sum or difference.
5 9
4 5
1 2
7 8
3 7
2.

3.

3 4
1 5

9
4.
6
4
5.
Decide if you need an exact answer or if an
estimate is sufficient. Janet needs 4 quarts of
oil for her car. If she has 2 quarts, how
much more does she need?
1 2
1 2
An estimate is sufficient.