Lesson 8

Calculating Products of Decimals

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Problem 1

Here are an unfinished calculation of \((0.54) \boldcdot (3.8)\) and a 0.54-by-3.8 rectangle.

An unfinished calculation of 0 point 54 times 3 point 8. 0 point 54 times 8 equals 0 point 432. 0 point 54 times 3 equals 1 point 62.
Rectangle divided into sections. Longer rectangle width 0 point 54 and length 3. Shorter rectangle length 0 point 8.
  1. Which part of the rectangle has an area of 0.432? Which part of the rectangle has an area of 1.62? Show your reasoning.
  2. What is \((0.54) \boldcdot (3.8)\)?

Solution

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Problem 2

Explain how the product of 3 and 65 could be used to find \((0.03) \boldcdot (0.65)\).

Solution

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Problem 3

Use vertical calculation to find each product.

  1. \((5.4)\boldcdot (2.4)\)
  2. \((1.67)\boldcdot (3.5)\)

Solution

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Problem 4

A pound of blueberries costs $3.98 and a pound of clementines costs $2.49. What is the combined cost of 0.6 pound of blueberries and 1.8 pounds of clementines? Round your answer to the nearest cent.

Solution

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Problem 5

Complete the calculations so that each shows the correct sum or difference.

2 decimal addition problems and 1 decimal subtraction problem.

Solution

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(From Unit 5, Lesson 3.)

Problem 6

Which has a greater value: \(7.4 - 0.0022\) or \(7.39-0.0012\)? Show your reasoning.

Solution

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(From Unit 5, Lesson 4.)

Problem 7

Andre is planting saplings (baby trees). It takes him 30 minutes to plant 3 saplings. If each sapling takes the same amount of time to plant, how long will it take Andre to plant 14 saplings? If you get stuck, consider using the table.

number of saplings time in minutes
3 30
1
14

Solution

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(From Unit 2, Lesson 12.)