To the Left, to the Left...
Adding Zeros
2 x 1
2 x 2
Peanut Butter, Unicorns, Santa
100

When you multiply a number by 0.1, which direction do the digits shift?

To the left!

100

20 x 10 = 2,000.  True or False?

False!  20 x 10 = 200

100

34 x 7 =

238

100

2.2 x 34 = 

74.8

100

32 x 49 = approximately what when I round?  

30 x 50 = 1,500

200
When you multiply a number by 0.01, which direction and how many places do the digits shift?

To the left, two places!

200

50 x 40 = 200.  True or False?

False.  50 x 40 = 2,000

200

52 x 9 =

468

200

3.4 x 5.6 =

19.04

200

Sam estimated his answer to be 4,800 when he multiplied 51 x 39.  Is this reasonable?  

No.  51 x 39 should be rounded to 50 x 40 = 2,000.  

300

When you multiply a number by 100, which direction do the digits shift?

To the right!

300

What is 60 x 400?  

24,000

300

6.2 x 3 =

18.6

300

0.24 x 0.31 = 

0.0744

300

Tony estimated her answer to be 32,000 when she estimated 789 x 41.  Is this reasonable?  

Yes.  789 x 41 rounds to 800 x 40 = 32,000.

400

You multiplied a number by .0001.  What direction, and how many places did the digits shift?

4 places to the left!

400

20 x 30 x 40 =

24,000

400

0.28 x 9 =

2.52

400

An Atlas Moth has a wingspan of 11 inches.  How wide would the wingspans of 73 Atlas Moth's be?

803 inches.

400

Round and Estimate 37 x 63.  

40 x 60 = 2,400

500

Use shifting patterns, what is 345 x 0.01?  

3.45

500

Which one does not equal 32,000?  80 x 400.  8 x 4,000.  800 x 40.  8,000 x 40.

8,000 x 40.

500

3.4 x 0.6 =

2.04

500

Mike wants to save $400 for some new clothes.  He makes $22 an hour and worked 19 hours.  Did he save enough to reach his goal? 

Yes.  He saved $418!

500

Name one place you see decimals every day.  

Gas station.  Money.  

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