SAT Math Multiple Choice Practice Question 436: Answer and Explanation

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Question: 436

19. The value of the nth term of a sequence is given by the expression a3n – 3. If the second term of the sequence is 61, which of the following could be the value of a ?

I. –2

II. 2

III. 4

A. I only
B. II only
C. III only
D. I and II only
E. II and III only

Correct Answer: D


D Because 61 is the value of the second term in the sequence, plug in 2 for n: a3(2) – 3 = 61. Therefore, a6 = 64, and a must be equal to ±2. Make sure you read carefully; III would work if 61 were the value of the first term.

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