1. Estimate with Fractions
4-9
Estimate with Fractions
Course 2
Warm Up
Problem of the Day
Lesson Presentation

2. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
Warm Up
Divide. Write each answer in simplest form. 3 10 13 1 3 40 or
1. 4 ÷ 3 4 6 5 ÷ 5 8 2. 2 3 5 6 18 4 5 94 or 3. 15 ÷

3. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
Problem of the Day
Fill in the square using the numbers 5–13 so that all sums (rows, columns, and main diagonals) are the same. 8 13 6 7 9 11 12 5 10

4. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
Learn to estimate sums and differences of fractions and mixed numbers.

5. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
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 1 2 2 5

6. Guidelines for Rounding Fractions
Course 2
4-9
Estimate with Fractions
You can also round fractions by comparing
numerators with denominators.
Guidelines for Rounding Fractions 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: 1 9 3 20 2 11
, , 2 5 12 7 13
, , 23 25 97
100 8 9
, ,

7. Estimating with Fractions Insert Lesson Title Here
Course 2
4-9
Estimating with Fractions
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? 33 3 5 – 4 1 2 33 3 5 33 1 2 4 1 2 4 1 2
Round each mixed
number.
= 29 – 33 1 2 4
Subtract.
The blue whale is about 29 m longer.

8. Insert Lesson Title Here
Course 2
4-9
Estimating with Fractions
Insert Lesson Title Here
Try This: Example 1
A Cocker Spaniel may grow to weigh about kilograms while the Chihuahua will not weigh more than 2 kilograms. About how much more can a Cocker Spaniel weigh? 1 2 7 8 11 1 2 – 7 8 11 1 2 11 1 2 2 7 8
Round each mixed
number. 3
= 8 – 11 1 2 3
Subtract.
The Cocker Spaniel weighs about 8 kg more. 1 2

9. Additional Example 2A & 2B: Estimating Sums and Differences
Course 2
4-9
Estimate with Fractions
Additional Example 2A & 2B: Estimating Sums and Differences
Estimate each sum or difference. 7 9 1 5 A. – 7 9 1 5 1
Round each fraction.
1 – 0 = 1
Subtract. 5 9 B. 4 + 3 1 8 4 5 9 4 1 2 3 1 8 3
Round each mixed fraction. 4 1 2 + 3 = 7
Add.

10. Additional Example 2C: Estimating Sums and Differences
Course 2
4-9
Estimate with Fractions
Additional Example 2C: Estimating Sums and Differences
Estimate the sum. 1 8 7 12 C. –2 + –2 1 8 7 12 1 2 –2
Round each number. 1 2 + = –1 –2
Add.

11. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
Try This: Example 2A & 2B
Estimate each sum or difference. 7 8 1 6 A. – 7 8 1 6 1
Round each fraction.
1 – 0 = 1
Subtract. 3 5 B. + 2 9 5 3 5 1 2 2 9 2
Round each mixed fraction. 5 1 2 + = 7
Add.

12. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
Try This: Example 2C
Estimate the sum. 2 9 8 15 C. –4 + –4 2 9 8 15 1 2 –4
Round each number. 1 2 + = –3 –4
Add.

13. Estimate with Fractions
Course 2
4-9
Estimate with Fractions
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.
Words like about and around signal that an exact answer is not necessary.
Helpful Hint

14. Estimate with Fractions Insert Lesson Title Here
Course 2
4-9
Estimate with Fractions
Insert Lesson Title Here
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.

15. Additional Example 3B: Deciding If an Estimate is Enough
Course 2
4-9
Estimate with Fractions
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.

16. Insert Lesson Title Here
Course 2
4-9
Estimate with Fractions
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 .

17. Insert Lesson Title Here
Course 2
4-9
Estimate with Fractions
Insert Lesson Title Here
Try This: Example 3B
Decide if you need an exact answer or if an estimate is enough.
William’s 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.

18. Estimating with Fractions Insert Lesson Title Here
Course 2
4-9
Estimating with Fractions
Insert Lesson Title Here
Lesson Quiz
1. The new show arena being built in Franklin County is feet long and 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 2. + 3. 7 8 3 7 1 2 – 3 4 1 5 4. 9 – 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.