4-2 Estimate Products of Decimals and Whole Numbers

Estimate 0.12 x 105

• Answer: 0

  0.12 ≈ 0

  105 ≈ 100

  0 x 100 = 0

• Answer: 1200

  0.12 ≈ 12

  105 ≈ 100

  12 x 100 = 1200

• Answer: 12

  0.12 ≈ 0.12

  105 ≈ 100

  0.12 X 100 = 12

• Answer: 1000

  0.12 ≈ 10

  105 ≈ 100

  10 x 100 = 1000

Estimate 45.3 x 4

• Answer: 45.3

  45.3 ≈ 45

  4 ≈ 1

  45 x 1 = 45

• Answer: 180

  45.3 ≈ 45

  4 ≈ 4

  45 x 4 = 180

• Answer: 1,812

  45.3 ≈ 453

  4 ≈ 4

  453 x 4 = 1,812

• Answer: 2000

  45.3 ≈ 500

  4 ≈ 4

  500 x 4 = 2000

Estimate 99.2 x 82

• Answer: 8000

  99.2 ≈ 100

  82 ≈ 80

  100 x 80 = 8000

• Answer: 110000

  99.2 ≈ 100

  82 ≈ 100

  100 x 100 = 110000

AGAIN Estimate 99.2 x 82

• Answer: 82100

  99.2 ≈ 100

  82 ≈ 82

  100 x 82 = 82100

• Answer: 8200

  99.2 ≈ 100

  82 ≈ 82

  100 x 82 = 8200

Estimate 37 x 0.93

• Answer: 37

  37 ≈ 37

  0.93 ≈ 1

  37 x 1 = 37

• Answer: 0

  37 ≈ 37

  0.93 ≈ 0

  37 x 0 = 0

• Answer: 3700

  37 ≈ 37

  0.93 ≈ 100

  37 x 100= 3700

Select the estimate that WOULD NOT WORK for 1.67 X 4

• 8

• 4

• 6

Select the estimate that WOULD NOT WORK for 3.2 x 184

• 3 x 150 = 450

• 32 x 100 = 3200

• 3 x 200 = 600

What is the best estimate for 0.37? 0.50 or 1?

• 1

• 0.50 or half

Select the estimate that WOULD BE LEAST LIKELY TO WORK for 0.904 x 75

• Answer: 0

  0.904 ≈ 0

  75 ≈ 75

  0 x 75 = 0

• Answer: 75

  0.904 ≈ 1

  75 ≈ 75

  1 x 75 = 75

• Answer: 80

  0.904 ≈ 1

  75 ≈ 80

  1 x 80 = 80