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A: Numbers of Triangles

Correct Response

• 18 AND 32

Incorrect Responses

• 18 and any number other than 32
• 18 and no numerical response for the 4th figure
• Other incorrect

B: Number of Triangles in Figure 7

Correct Response

• 98

Incorrect Responses

• 49 [Multiplies 7 x 7]
• 58 [Series is 2, 8, 18, 28, 38…7th term is 58]
• Other incorrect

C: Explanation for Extending to the 50th Figure

Correct Responses

• Correct general (i.e., literal) expression, e.g., 2n2 , or equivalent expressed in words
• 2 x 502 OR 2 x 50 x 50 OR 100 x 50 OR (50 + 50) x 50 OR equivalent expressed in words (disregard errors in computation)

Partial Responses

• Derives answer (5000) without showing work
• Other partially correct

Incorrect Responses

• 50 x 2 OR 100
• 50 x 50 OR 2,500
• Other incorrect

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