Multiplying Decimals Review

Powers of 10

100

0.8 x 10

8

200

.77 x 10²

77

300

2.43 x 10¹

24.3

400

0.008 x 10²

0.8

500

0.10004 x 10³

100.04

Estimation

100

Estimate: 1.2 x 8.4

Overestimate or Underestimate?

1 x 8 = 8

Underestimate

200

Estimate: 9.8 x 47 

Overestimate or Underestimate?

10 x 47 = 470

Overestimate

300

Estimate: 27.6 x 65.5

Overestimate or Underestimate?

30 x 70 = 2100

Overestimate

400

Estimate: 0.3 x 8.6

Overestimate or Underestimate?

1 x 9 = 9

Overestimate

500

Estimate: 2.1 x 147.3

Overestimate or Underestimate?

2 x 150 = 300

Overestimate

Standard Algorithm

100

15 x 0.5

7.5

200

0.3 x 1.5

0.45

300

6.7 x 4.8

32.16

400

7.18 x 5.3

38.054

500

0.29 x 34.2

9.918

Story Problems

100

One study guide is 0.066 cm thick. How thick would a stack of 100 study guides be?

6.6 cm thick

200

Suzie Q. rides her bike 3.54 miles to and from her friend's house. Estimate the total distance Suzie Q. rode her bike after 28 visits. 

Overestimate or Underestimate?

4 x 30 = 120 miles

Overestimate

300

The pond in front of ASCS is 0.3 square miles, and 0.7 of the pond has lily pads. How many square miles is the lily pad area?

0.21 square miles

400

It costs $395 an hour to rent out a screen at the movie theater. How much would it cost for the 5th graders to rent a screen for 2.5 hours?

$987.50

500

Suzie Q. made a square canvas painting for art class. Each of the four sides measures 12.5 inches. How much is the total perimeter of Suzie Q.'s painting?

50 inches

Story Problems But They Are Different, Yet the Same

100

One whiteboard is 0.54 inches. How many inches would 100 whiteboards be?

54 inches

200

Billy Bob rollerbladed 2.78 miles from ASCS to his house every WEEKDAY for three weeks. How many miles did Billy Bob rollerblade in all?

41.7 miles

300

Suzie Q. rented a camera for her photography class. It costs $0.24 per minute to rent. Suzie Q. used the camera for 39.5 minutes. How much money does she owe for borrowing the camera?

$9.48