Do Now 11/16/11

1
Do Now 11/16/11

• Take out your HW from last night.
• Text p. 106, 10-44 evens
• Copy HW in your planner.
• Text p. 110, 14-34 evens
• Quiz sections 3-1 to 3-3 Friday
• In your journal, divide the following numbers.
  Describe any patterns you see in the 4 problems.

900 300
90 30
9 3
0.9 0.3
2
Homework Text p. 106, 10-44 evens

• 10) 4.8
• 12) -8.1
• 14) 29.4
• 16) 90.73
• 18) 7.68
• 20) 24.38
• 22) -0.1542
• 24) -40.945
• 26) 284.4 km
• 28) -19.68

• 30) 16.6
• 32) -0.0876
• 34) -488.85
• 36) 30.495
• 38) -0.7728
• 40) 319.63
• 42) a. yes
• b. about 42 million people
• 44) 21.5124

3
Objective

• SWBAT divide decimals

4
Section 3-3 Dividing Decimals
How do you divide two decimal numbers
0.6 0.3
0.3 0.6
or
divisor
By multiplying both numbers by the same power of
ten, you can make the divisor an integer.
Dividing by an integer is much easier than
dividing by a decimal.
2
0.3 0.6
Multiply both numbers by 10
3 6
5
Find the quotient of 0.246 0.03
Multiply both numbers by 100 to make the
divisor an integer
0.03 0.246
3 24.6
8
2
Move the decimal point straight up, then divide
as you normally would.
.
24 6
3
24
0 6
6
Finished
6
Find the quotient of 7.75 1.25
Multiply both numbers by 100 to make the
divisor an integer
1.25 7.75
125 775
6
2
Move the decimal point straight up, then divide
as you normally would.
775
125
0
.
750
25
250
Finished
7
Dividing Integers
Remember this?

• Rule 1
• The quotient of two integers with the same sign
  is always POSITIVE!
• 8 2 4 -18 (-3) 6
• Rule 2
• The quotient of two integers with different
  signs is always NEGATIVE!
• -6 3 -2
  28 (-4) -7

8
Negative or Positive?

• Without solving the problem, decide whether the
  quotient will be positive, negative, or zero.
  Then estimate the answer to the nearest integer.

-8.2 (-4.36)
-23.3 11.76
negative
positive
-3.3 3.3
-17.9 (-6.02)
negative
positive
9
Find the quotient of -11.2 0.8
Multiply both numbers by 10 to make the divisor
an integer
0.8 11.2
8 112
-
1
4

• The quotient of two integers with different signs
  is always NEGATIVE!

.
11
8
2
8
3
32
Finished
10
Find the quotient of -0.875 (-0.25)
Multiply both numbers by 100 to make the
divisor an integer
0.25 0.875
25 87.5
3
5
Move the decimal point straight up, then divide
as you normally would.
.
87
25
5
75
The quotient of two integers with the same sign
is always POSITIVE!
12
125
Finished
11
Find the quotient of -9 1.25
Multiply both numbers by 100 to make the
divisor an integer
1.25 9.00
125 900
-
7
2
Move the decimal point straight up, then divide
as you normally would.
.
900
125
0
875

• The quotient of two integers with different signs
  is always NEGATIVE!

25
250
Finished
12
Real-Life

• If Sandy and her family used 14.95 gallons of
  gas to drive 358.8 miles, how many miles per
  gallon did the car get?

Multiply both numbers by 100 to make the
divisor an integer
14.95 358.8
24
1495 35880
The car got 24 miles per gallon
13
24
Homework
Text p. 110, 14-34 evens