Problem Solving

Official Guide

A set of number has the property that for any number t, t+2 is in the set. If -1 is in the set, which of the following must also be in the set?

I. -3
II. 1
III. 5

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

OA D

A set of number has the property that for any number t, t+2 is in the set. If -1 is in the set, which of the following must also be in the set?

I. -3
II. 1
III. 5

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

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Answer:
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This means that the set MUST include all the odd numbers that are greater than -1
Therefore, 1 & 5 must be in the set, while -3 might or might not be in the set because it is less than -1
So the Answer is D