saikiranx wrote:

If x and y are positive integers such that the product of x and y is prime, what is the units’ digit of 7x + 9y?

(1) 24 < y < 32

(2) x = 1

(A) Statement (1) ALONE is sufficient to answer the question, but statement (2) alone is not.

(B) Statement (2) ALONE is sufficient to answer the question, but statement (1) alone is not.

(C) Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient.

(D) EACH statement ALONE is sufficient to answer the question.

(E) Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question.

I do not agree with the OA. Answer should be E.

From the question statement, we can see that one of the numbers is 1 and the other is a prime.

1)We get x=1, y can be 29 or 31. If it is 29, units digit of expression is 8. If it is 31, units digit of expression is 6. Insufficient.

2) Obviously insufficient. As illustrated from statement 1.

Answer is hence E.

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