Section C Section C Checkpoint

Problem 1

Find the value of the expression $0.3 \times 0.5$ . Explain or show your reasoning. Use the grid if it is helpful.

<p>Diagram, square. Length and width, 1. Partitioned into 10 rows of 10 of the same size squares. No squares shaded. </p>

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Solution

0.15. Sample response: There are 15 shaded parts and each one is 0.01.

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Sample Response

0.15. Sample response: There are 15 shaded parts and each one is 0.01.

Problem 2

To find the value of $0.28 \times 37$ Andre calculates $28 \times 37$ and then multiplies by 0.01. Explain or show why Andre's strategy works and use it to find the value of $0.28 \times 37$ .

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Solution

10.36. Sample response: Since 0.28 is 28 hundredths, I can multiply 28 and 37 and then multiply that by 0.01. Since $28 \times 37 = 1,036$ , $0.28 \times 37$ is $10.36$ .

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Sample Response

10.36. Sample response: Since 0.28 is 28 hundredths, I can multiply 28 and 37 and then multiply that by 0.01. Since $28 \times 37 = 1,036$ , $0.28 \times 37$ is $10.36$ .

Problem 3

Find the value of the expression

2.1 \times 7.3

. Explain or show your reasoning.

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Solution

15.33. Sample response: I first found $21 \times 73$ which is $1,533$ . Then I multiply that by 0.1 twice since $2.1 = 21 \times 0.1$ and $7.3 = 73 \times 0.1$ . That gives $15.33$ .

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Sample Response

15.33. Sample response: I first found $21 \times 73$ which is $1,533$ . Then I multiply that by 0.1 twice since $2.1 = 21 \times 0.1$ and $7.3 = 73 \times 0.1$ . That gives $15.33$ .