EgmatQuantExpert wrote:
e-GMAT Question:
If \(X\) is a positive integer, what is the units digit of \(X^a\)?
1) \(X\) when divided by \(10\) gives a remainder of \(2\)
2) \(8^a\) ends with \(6\)
A) Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B) Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D) EACH statement ALONE is sufficient.
E) Statements (1) and (2) TOGETHER are NOT sufficient
Given: X > 0
Units digit of X^a
St 1: X = 2, 12, 22, and Units digit of X^a can be 2, 4, 8, 6.
Insufficient, no information about "a"
St 2: \(8^a\) ends with \(6\) means "a" is a multiple of "4" , but we don't know about "X"
InsufficientCombining we get unit digit of X^a will be "6" as every 4th power of 2 or 12 or 22 will give you units digit "6"
(C)
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72% (01:22) correct 
