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Bunuel
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Given in the question:-

Machines A, B, and C working together can finish a job in 24 hours.

So their combined rate is:
1/24 of the job per hour.
Let the work done by A, B and C alone is:

  1. A’s rate = 1/a jobs/hour
  2. B’s rate = 1/b jobs/hour
  3. C’s rate = 1/c jobs/hour
[*] Then,
[*] 1/a + 1/b + 1/c = 1/24
[*] Now checking the statements:-
Statement (1): Machines B and C together can complete the job in 36 hours.
So: 1/b + 1/c = 1/36
Now subtract this from the total rate: (1/a + 1/b + 1/c)−(1/b + 1/c)=1/24−1/36
[*] 1/a = 1/24-1/36
[*]
Find common denominator (72): 1/a=(3−2)/72=1/72
[*] So a = 72
[*] Using statement (1) alone, we can find A’s time.
[*] Hence, Statement (1) is sufficient.
[hr]
Statement (2): Machines A and C together can complete the job in 48 hours.
So: 1/a+1/c=1/48
[*] We also know from the question: 1/a+1/b+1/c=1/24
[*] Subtract: (1/a+1/b+1/c)−(1/a+1/c)=1/24−1/48
[*] 1/b = 1/48
[*] That tells us B’s rate, but we still don’t know A’s rate.
[*] So we cannot find A’s time from this alone.
[*] Statement (2) is not sufficient.
[hr]
Final Answer:
Statement (1) alone is sufficient, but statement (2) alone is not.
Answer: (A)
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