Transcript File

3-3 Dividing Decimals
Multiply.
Do Now
1. 24.5  7
171.5
2. 5.4  -6.2
-33.48
3. (-19.21)  (–2.1)
40.341
3-3 Dividing Decimals
Learn to divide decimals.
3-3 Dividing Decimals
In order to divide BY a decimal, the decimal
divisor must be changed into an integer.
To change a decimal divisor, move the decimal
point all the way to the right, noting how many
places you had to move it (what you are really
doing is repeatedly multiplying by 10).
Now, change the dividend by moving the decimal
point the same number of times. THE DIVIDEND
MAY STILL BE A DECIMAL NUMBER.
3-3 Dividing Decimals
The rules regarding negative decimals is the
same as with integers:
Both signs same – quotient is positive
One positive and one negative – quotient is
negative
3-3 Dividing Decimals
Example A
Divide.
8.28 ÷ 4.6
8.28 ÷ 4.6 = 82.8 ÷ 46
1.8
46) 82.8
– 46
36 8
–36 8
Multiply both numbers by 10 to
make the divisor an integer.
Divide as with whole numbers.
0
Helpful Hint
Multiply both numbers by the least power of ten that will
make the divisor an integer.
3-3 Dividing Decimals
Example A
Divide.
18.48 ÷ (–1.75)
18.48 ÷ (–1.75) = 1848 ÷ 175 Multiply both numbers by 100
to make the divisor an integer.
1 0.5 6
Use zeros as placeholders
175 ) 1848 . 00
Divide as with whole
–175
numbers.
98 0
–87 5
10 50
–10 50
0
18.48 ÷ (–1.75) = –10.56
The signs are different.
3-3 Dividing Decimals
Example A
Divide.
–24 ÷ (–2.5)
–24.0 ÷ (–2.5) = –240 ÷ (–25)
9. 6
25 ) 240 .0
– 225
15 0
– 15 0
0
Multiply both numbers by 10.
Divide as with whole numbers.
3-3 Dividing Decimals
Example B
Jace took a trip in which he drove 350 miles.
During the trip his truck used 12.5 gallons of
gas. What was his truck’s gas mileage?
350.0 ÷ 12.5 = 3500 ÷ 125
28
125) 3500
–250
1000
–1000
0
Multiply both numbers by 10.
Divide as with whole numbers.
Helpful Hint
To calculate miles per gallon, divide the
number of miles driven by the number
of gallons of gas used.
Jace’s truck’s gas mileage was 28 miles per gallon.
3-3 Dividing Decimals
Lesson Quiz
Divide. Estimate to check whether each
answer is reasonable.
1. 78.2 ÷ 0.04
1,995
2. –9.72 ÷ 2.7
–3.6
3. 18.88 ÷ 1.6
11.8
4. 19.5 ÷ 3.25
6
5. Jordan used 32.46 gallons of gas to drive his
van 584.28 miles. How many miles did Jordan get
per gallon? 18
3-3 Dividing Decimals
6. Divide.
87.3 ÷ 0.09
A. 873
B. 970
C. 977
D. 1230
3-3 Dividing Decimals
7. Divide.
–14.72 ÷ (3.2)
A. –4.6
B. –5
C. –5.2
D. –5.6
3-3 Dividing Decimals
8. Divide.
19.98 ÷ 1.8
A. 11.4
B. 11.3
C. 11.2
D. 11.1
3-3 Dividing Decimals
9. Divide.
17.15 ÷ 2.45
A. 7
B. 8
C. 9
D. 10
3-3 Dividing Decimals
10. Chris drives at an average speed of 55.45
miles per hour. How long does it take for
him to travel a distance of 388.15 miles?
A. 6 hours
B. 7 hours
C. 8 hours
D. 9 hours