Section A Section A Checkpoint

Problem 1

Find the value of each sum. Use an algorithm or a strategy of your choice.

  1. 375+444375+444
  2. 138+283138+283
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Solution

  1. 819. Sample response:

    300+400=700300 + 400 = 700
    70+40=11070 + 40 = 110
    5+4=95+4 = 9
    700+110+9=819700 + 110 + 9 = 819

  2. 421. Sample response:

    <p>Addition.</p>

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Sample Response

  1. 819. Sample response:

    300+400=700300 + 400 = 700
    70+40=11070 + 40 = 110
    5+4=95+4 = 9
    700+110+9=819700 + 110 + 9 = 819

  2. 421. Sample response:

    <p>Addition.</p>

Problem 2

Here is how Han found the value of 684+237684 + 237.

Add. Six hundred eighty-four plus two hundred thirty-seven equals nine-hundred twenty-one.

  1. What is the meaning of the two 1s above 684 in Han's calculation?
  2. Explain why Han's strategy accurately finds the value of 684 + 237.
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Solution
Sample responses:
  1. The 1 above the 8 is a ten coming from 4+74+7, which is a ten and a one. The 1 above the 6 is a hundred, which comes when Han adds up the tens in the sum.
  2. He adds the ones, tens, and hundreds of the two numbers, and the two 1s help him add them all up correctly.
Show Sample Response
Sample Response
Sample responses:
  1. The 1 above the 8 is a ten coming from 4+74+7, which is a ten and a one. The 1 above the 6 is a hundred, which comes when Han adds up the tens in the sum.
  2. He adds the ones, tens, and hundreds of the two numbers, and the two 1s help him add them all up correctly.