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Do Now 11/15/11 PowerPoint PPT Presentation

Do Now 11/15/11. Take out your HW from last night. Text p. 102, #10-40 evens, #42, 43, 48, & 49 Copy HW in your planner. Text p. 106, #10-44 evens

Do Now 11/15/11

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Do Now 11/15/11

• Take out your HW from last night.

• Text p. 102, #10-40 evens, #42, 43, 48, & 49

• Copy HW in your planner.

• Text p. 106, #10-44 evens

• In your journal, estimate an answer to the following situation. Potato salad costs \$0.99 per pound at the deli counter. About how much do you think 6.5 pounds of potato salad will cost?

10) 39.05

12) 16.917

14) 15.33

16) 9.071

18) 2.24

20) 12.79

22) 4.47

24) 31.15

26) 8.25 minutes

28) -0.338

30) -17.361

32) -125.55

34) 48.46

36) 30.623

38) -2.6

40) 1,642.5 miles

42) 1.6 °F

43) 1915

48) B

49) G

Objective

• SWBAT multiply decimals

Section 3-2Multiplying Decimals

To multiply decimals, multiply as you would integers. To place the decimal point in the product count the number of decimal places in each factor. The product will have the same number of decimal places as the sum of the decimal places in the factors.

Find the product. 3.06 x 1.4

3.06

2 decimal places

How many

decimal places

are in

each number?

x 1.4

1 decimal place

1224

How many

decimal places

are in the sum of

both numbers?

+3060

4284

4.284

3 decimal places will then be in the product!

Do you see a pattern?

How many decimal places are in the factors?

12

1.2

0.12

x 4

x 0.4

x 4

48

4.8

48

000

How many decimal places are in the products?

0.048

Practice

• 1) 1.46 x 0.02

• 2) 3.04 x 1.6

1)1.46

x 0.02

0.0292

2)3.04

x 1.6

1824

_+3040

4.864

“Multiplying Integers”

Remember this?

Rule #1

The product of two integers with the same sign is always POSITIVE!

8 x 3 = 24 -8 · (-7) = 56

Rule #2

The product of two integers with different signs is always NEGATIVE!

-6 x 3 = -18 8(-4) = -32

Estimating

Round each decimal to the nearest integer than find the product.

-11.3 x 7.76

7.2(-4.36)

-88

-28

-7.3(-6.72)

-3.3(-3.3)

9

49

Find the product. -2.78 · 0.8

-2.78

2 decimal places

How many

decimal places

are in

each number?

x 0.8

1 decimal place

-2.224

-2224

How many

decimal places

are in the sum of

both numbers?

3 decimal places will then be in the product!

0.014

Find the product. -16 x 0.014

3 decimal places

How many

decimal places

are in

each number?

x -16

0 decimal places

0084

How many

decimal places

are in the sum of

both numbers?

+0140

-0.224

-0224

3 decimal places will then be in the product!

“Real-Life”

On average, Americans eat 0.25 lb of peanut butter per month. How many pounds of peanut butter are eaten by approximately 302 million Americans living in the United States per month?

302

x 0.25

1510

6040

75.50

million pounds of peanut butter are eaten by Americans each month

24

Homework

Text p. 106, #10-44 evens