Multiplying Decimals

Multiplying Decimals

Step 1

• Round any decimal to the nearest whole number

• Multiply the whole numbers to get an estimate

Multiple Choice

Josie bought 3 packs of gum that were $3.19 each. If we are rounding to the nearest whole number, what do we round $3.19 to?

• $3

• $4

• $3.50

• $1

Multiple Choice

Yes--$3!

Now what is our ESTIMATE for our gum purchase (3 packs of gum at approximately $3 each?

• $1

• $3

• $9

• $6

Step 2

• Now we know our "real" answer should be about $9

• Go back to the original problem and multiply, as if the decimals were not there.

• 3.19 x 3

Multiple Choice

What DIGITS do you get to the multiplication problem? (Remember, we have not yet put the decimal point into the answer)

• 9327

• 957

• 9527

• 937

Step 3

• Place your decimal point, according to your estimate

• Our estimate was $9

• Hopefully, the DIGITS you calculated resulted in: 957

• WHERE do we place our decimal point?

Multiple Choice

How much did Josie pay for 3 packs of gum that were $3.19 each?

• $9.57

• $.957

• $95.70

• $95.07

Multiple Choice

Kelly ran 3.85 miles each day for 5 days in a row. If we round to the nearest whole number, what do we round 3.85 to?

• 3

• 4

• 3.9

• 20

Multiple Choice

We should round 3.85 to 4 Based on that, what is our ESTIMATE for Kelly's 5 days of running?

• 4 miles

• 5 miles

• 9miles

• 20 miles

Multiple Choice

Go back and multiply 3.85 (5)

What DIGITS did you get? (Remember--no decimal points, yet)

• 1845

• 1925

• 15425

• 1565

Multiple Choice

1925 are the digits I hope you got!

Now--using our estimate of 20 miles, what was the total for Kelly's 5 days of running?

• 1.925 miles

• 19.25 miles

• 192.5 miles

• 1925 miles

Multiple Choice

What is your estimated answer for: 9.4 x 7

• 16

• 17

• 63

• 70

Multiple Choice

What are your DIGITS for:

9.4 x 7?

• 658

• 6328

• 6528

• 638

Multiple Choice

What is the product of 9.4 x 7?

• .658

• 6.58

• 65.8

• 658

Poll

The BEST part of this time of year is:

• Snow

• Math class, obviously:)

• Holiday celebrations

• Yummy food

Multiple Choice

Find the product of:

11.9 x 4

• 48

• 47.6

• 4.76

• 476

Multiple Choice

Find the product of:

7.3 x 8

• 58.4

• 56.24

• 5.84

• 584

Multiple Select

Choose ALL that apply:

To multiply decimals, I

• round decimals to the nearest whole number

• multiply to get an estimate

• spin around 11 times until I am dizzy

• place the decimal point in my final answer, using my estimate

Fill in the Blanks

Find the product of 32.3 x 5

Fill in the Blanks

Find the product of (17.9)(7)

Fill in the Blanks

32.8 $\cdot$  9

Fill in the Blanks

123.2(7)

Poll

I feel like:

• I need some extra help on decimal placement in my answer

• I need some additional assistance on the algorithm

• I need 227 practice problems for homework to fully understand this

• I have a good grasp on the introduction of decimal multiplication

Multiple Choice

My best ESTIMATE of 49.7 $$\cdot$$  6.2 is:

• 300

• 308.14

• 350

• 240