Multiplying and Dividing by powers of ten http://hench-maths.wikispaces.com

Warm UP Write each in standard form. Ten and thirty-eight hundredths Two hundred and five thousandths Write each decimal in words. 3. 25.9 4. 2.112

Warm Up

Warm Up Solve 1. 2. 3. 4.

Standards MGSE5.NBT.2 Explain patterns in the placement of decimal points when multiplying or dividing by powers of ten.

Essential Questions How can you represent a decimal using base 10 blocks? How can you multiply decimals by powers of ten?

Vocabulary Words Place Value – The value of a digit depending on its place in a number. Base Ten System – A number system based on tens. Power of Ten – The number of times ten is multiplied by itself.

PLACE VALUES of the digits in this number? 5 3 7 4 8 2 What are the PLACE VALUES of the digits in this number?

5 3 7 4 8 2 So that means 500 + 30 + 7 + + +

just separates the whole numbers from the decimal fractions 5 3 7 4 8 2 The decimal point just separates the whole numbers from the decimal fractions

What happens when I multiply this number by 10 ? 5 3 7 4 8 2 What happens when I multiply this number by 10 ?

5 3 7 4 8 2 Each digits value will become 10 times bigger so the digits move LEFT into the next column

Multiplying by 10 537.482 x 10 = 5374.82 It LOOKS like the decimal point moves one place to the right. (and that is how many teachers ask you to think of it)

Multiplying by 10 Moving the digits one place to the LEFT looks the same as moving the decimal point one place to the RIGHT. 5 3 7 4 8 2 5 3 7 4 8 2

More Multiplying and Dividing Digits Move ( LOOKS LIKE ) Decimal Point Moves x10 One place to LEFT One place to RIGHT x100 Two places to LEFT Two places to RIGHT ÷ 10 ÷ 100

I hope I haven’t LEFT you confused but I thought we should get this RIGHT Thanks for watching.

Ticket Out the Door 1. 2. 3. 4.