Multiplying and Dividing Decimals by Powers of Ten

When you multiply decimals by powers of ten,

• take a good guess

• smile, chances are you'll get one right

• use the Zero Rule and pretend the decimal isn't there

• there's a short cut to use if you understand, we have a base ten math system

Find the example of a question where you would use the Zero Rule

• 42 x 19

• 40 x 1.5

• 400 x 20

• 4.56 x 1,000

When you multiply decimals by powers of ten,

• add as many zeroes as you see

• count the number of zeroes

• move the decimal, however many zeroes are in the power of ten number

• move the decimal wherever you want

Solve. 3.40 x 100

• 3.40

• 34.0

• 340

• 3,400

How do you know which direction to move the decimal?

• Guess! You have a 50% chance of getting it right

• It doesn't matter. Math has many right answers.

• Sing the song!

• Ask your teacher.

Which way do you move the decimal when you multiply by powers of ten?

• to the left

• to the right

Which way do you move the decimal when you divide by powers of ten?

• to the right

• to the left

Solve: 0.08 x 10,000

• .08

• 80

• 800

• 8,000

Solve: 50 x 3,000

• 15,000.0

• 150.00

• 1,500,000

• 150,000

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