3.MD.C.7b- Relate Area to Multiplication_Reed's Square

3.MD.C.7b- Relate Area to Multiplication- Flawed Reasoning

Evidence Statement 3.C.4-5 Distinguish correct explanation/reasoning from that which is flawed, and if there is a flaw in the argument, present corrected reasoning. (For example, some flawed student thinking is presented and the task is to correct and improve it.)

Reed's Square

Reed thinks that the area of the square is 28 square inches because 4 x 7 = 28.

This image is a square with one side labeled 7 inches.

Part A

Explain why Reed’s thinking is incorrect.

Enter your explanation and answer below.

Part B

Find the correct area of the square using an equation.

Enter your answer and equation below.

Student Copy

Download: 3.MD.C.7b_Reeds_Square_Flawed_Reason_Hxv0aJk.docx

Scoring Rubric Part A

Score 1

Student response includes the following element.  

  • Reasoning component = 1 points
    • The student explains that Reed thought that since there were four sides he should multiply the 7 inches by 4. To find the area he should only multiply 2 side lengths.

Score 0

Student response is incorrect or irrelevant. 

Scoring Rubric Part B

Score 1

Computation component = 1 point 

  • The student provides the correct area and equation.
    • 7 x 7 = 49, The area of the square is 49 square inches.

Score 0

Student response is incorrect or irrelevant.

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