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In an arithmetic sequence of real numbers, the first term is 7 and each term after the first is 4 more than the preceding term. What is the value of the 10th term?
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Correct answer
D
In an arithmetic sequence the nth term equals the first term plus (n − 1) times the common difference. Here the first term is 7, the common difference is 4, and n is 10, so the 10th term is 7 + 9 × 4 = 7 + 36 = 43. The key is that going from the 1st term to the 10th takes 9 steps, not 10.
A counts only 7 steps, giving 35. B adds 9 steps of 4 but drops the first term, giving 36. C multiplies 4 by 10 and ignores the first term, giving 40. E counts 10 increments instead of 9, the classic off-by-one, giving 7 + 40 = 47. So the answer is D.
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