SAT Math Multiple Choice Practice Question 587: Answer and Explanation

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Question: 587

1. Which of the following could be the units digit of the cube of an integer?

I. 2

II. 6

III. 8

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

Correct Answer: E


E To answer this question, list some cubes of integers and see whether any of the digits in the statements turn up: 23 = 8, so we know that statement III is true. Eliminate A, B, and C because none of them contain III. Both of the remaining answers contain I, so it must be true. We need to check only statement II. List cubes until a 6 comes up in the unit's digit or until the unit's digit begins repeating: 33 = 27, 43 = 64, 53 = 125, 63 = 216 so II is true. Pick E.

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