Machine A and Machine B work at constant rates. How many hours does it take Machine A alone to complete a certain task?
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
Statements (1) and (2) TOGETHER are NOT sufficient.
✓ Correct Answer: Option C
Let R_A and R_B be the rates of Machine A and B respectively. Let T_A be the time for A alone. (1) R_A + R_B = 1/12 (work per hour). Insufficient. (2) R_A = 2R_B. Insufficient. Together: Substitute R_B = R_A/2 into (1): R_A + R_A/2 = 1/12. 1.5R_A = 1/12. R_A = (1/12) / 1.5 = 1/18. So, T_A = 1/R_A = 18 hours. Sufficient.
💡 Why is C) the correct answer?
The correct answer to the question "Machine A and Machine B work at constant rates. How many hours does it take Machine A alone to complete a certain task?" is Option C: BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient..
The other options — 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., D) Statements (1) and (2) TOGETHER are NOT sufficient. — are incorrect for this GMAT Exam Prep question. As explained above: Let R_A and R_B be the rates of Machine A and B respectively. Let T_A be the time for A alone. (1) R_A + R_B = 1/12 (work per hour). Insufficient. (2) R_A = 2R_B. Insufficient. Together: Substitute R…
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