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3-4 Dividing Decimals by Integers
Warm Up
Problem of the Day
Lesson Presentation
Course 2
3-4 Dividing Decimals by Integers
Warm Up
Multiply or divide.
1. 3.4  2.6
8.84
2. 6.25  5
31.25
3. 8.14  1.1 8.954
4. 825 ÷ 15
55
5. 756 ÷ 12
63
Course 2
3-4 Dividing Decimals by Integers
Problem of the Day
Divide 60 by 1 and add 10. What is your
answer?
130
Course 2
2
3-4 Dividing Decimals by Integers
Learn to divide decimals by integers.
Course 2
3-4 Dividing Decimals by Integers
Elena received scores of 6.85, 6.95, 7.2, 7.1, and
6.9 on the balance beam at a gymnastics meet. To
find her average score, add her scores and then
divide by 5.
6.85 + 6.95 + 7.2 + 7.1 + 6.9 = 35
35 ÷ 5 = 7
Elena’s average score was 7, or 7.0.
Notice that the sum of Elena’s scores is an integer.
But what if the sum is not an integer? You can find
the average score by dividing a decimal by a whole
number.
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3-4 Insert
Lesson
Titleby
Here
Dividing
Decimals
Integers
Remember!
Division can undo multiplication.
0.2 · 4 = 0.8 and
0.8 ÷ 4 = 0.2
0.8 ÷ 4
0.8 divided into 4 equal groups
The size of each group is the answer.
Each group is 2 columns, or 0.2.
0.8 ÷ 4 = 0.2
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3-4 Dividing Decimals by Integers
Additional Example 1A: Dividing Decimals by
Integers
Divide. Estimate to check whether each
answer is reasonable.
36.75 ÷ 7
5 .25
7 ) 36.75
–35
17
–14
35
–35
0
Estimate
35 ÷ 7 = 5
Course 2
Place the decimal point for the answer
directly above the decimal under the
division symbol.
Divide as with whole numbers.
5.25 is a reasonable answer.
3-4 Dividing Decimals by Integers
Remember!
0.6 ÷ 0.3 = 2
Dividend
Quotient
Divisor
2
0.3 ) 0.6
Course 2
3-4 Dividing Decimals by Integers
Additional Example 1B: Dividing Decimals by
Integers
Divide. Estimate to check whether each
answer is reasonable.
0.87 ÷ 3
Course 2
Place the decimal point for the answer
directly above the decimal under the
division symbol. Add a zero as a
placeholder in the answer.
0 .2 9
3 ) 0.87
–6
27
–27
0
Divide as with whole numbers.
Estimate
0.9 ÷ 3 = 0.3
0.29 is a reasonable answer.
3-4 Dividing Decimals by Integers
Remember!
When you divide two numbers with different
signs, the answer is negative.
Course 2
3-4 Dividing Decimals by Integers
Additional Example 1C: Dividing Decimals by
Integers
Divide. Estimate to check whether each
answer is reasonable.
82.08 ÷ (–27)
3 .0 4
The signs are different.
27 ) 82.08
–81
Think: 82.08 ÷ 27.
10
–0
Place the decimal point for the answer
1 08
directly above the decimal under the
–108
division symbol.
0
82.08 ÷ (–27) = –3.04
Estimate
90 ÷ –30 = –3
Course 2
The answer is reasonable.
3-4 Insert
Lesson
Titleby
Here
Dividing
Decimals
Integers
Check It Out: Example 1A
Divide. Estimate to check whether each
answer is reasonable.
39.16 ÷ 4
9 .79
4 ) 39.16
–36
31
–28
36
–36
0
Estimate
40 ÷ 4 = 10
Course 2
Place the decimal point for the answer
directly above the decimal under the
division symbol.
Divide as with whole numbers.
9.79 is a reasonable answer.
3-4 Insert
Lesson
Titleby
Here
Dividing
Decimals
Integers
Check It Out: Example 1B
Divide. Estimate to check whether each
answer is reasonable.
0.56 ÷ 4
Course 2
Place the decimal point for the answer
directly above the decimal under the
division symbol. Add a zero as a
placeholder in the answer.
0 .14
4 ) 0.56
–4
16
–16
0
Divide as with whole numbers.
Estimate
0.6 ÷ 4 = 0.15
0.14 is a reasonable answer.
3-4 Insert
Lesson
Titleby
Here
Dividing
Decimals
Integers
Check It Out: Example 1C
Divide. Estimate to check whether each
answer is reasonable.
65.16 ÷ (–12)
5 .4 3
The signs are different.
12 ) 65.16
–60
Think: 65.16 ÷ 12
51
–48
Place the decimal point for the answer
36
directly above the decimal under the
–36
division symbol.
0
65.16 ÷ (–12) = –5.43
Estimate
The answer is reasonable.
60 ÷ –12 = –5
Course 2
3-4 Dividing Decimals by Integers
Additional Example 2: Money Application
You can buy juice by the bottle or case. Either way,
it costs the same for each bottle. A case of 24
bottles of juice cost $23.52. Kevin bought a bag of
peanuts for 75¢ and one bottle of juice. How much
did Kevin spend in all?
First find the cost for one bottle of juice by dividing the
cost of a case by the number of bottles in a case. Then
add the cost of a bag of peanuts.
0 .98
24 ) 23.52
Place the decimal point for the answer
21 6
directly above the decimal under the
division symbol.
1 92
–1 92
0
One bottle of juice costs $0.98
$0.98 + $0.75 = $1.73
and a bag of peanuts costs $0.75
Kevin spent a total of $1.73.
Course 2
3-4 Insert
Lesson
Titleby
Here
Dividing
Decimals
Integers
Check It Out: Example 2
Cookies at a store sell for $1.80 a dozen. The cost for
each cookie is the same whether you buy them
individually or by the dozen. John decided to buy 1
cookie and a quart of milk. The milk costs $1.79. How
much did John have to pay?
First find the cost of one cookie by dividing the cost of a
dozen by 12. Then add the price for the milk.
0 .1 5
12 ) 1.80
Place the decimal point for the answer
12
directly above the decimal under the
division symbol.
60
– 60
0
One quart of milk costs
$1.79 + $0.15 = $1.94
$1.79 and one cookie
costs $0.15.
John spent a total of $1.94.
Course 2
3-4 Dividing
Insert Lesson
Decimals
Titleby
Here
Integers
Lesson Quiz
Divide. Estimate to check whether each
answer is reasonable.
1. 15.5 ÷ 5
3.1
2. 22.8 ÷ (–6) –3.8
3. 72.48 ÷ 24
3.02
4. 8.4 ÷ 12
0.7
5. Allison swam 5 sprint laps in the pool. If her
times were 17.5, 19.3, 20.6, 17.4, and 16.7
seconds per lap, what was her average lap time?
18.3 s
Course 2