A takes twice as much time as B and thrice as much as C to complete a job. By working together A, B and C can complete the job in 4 hours. Find the time taken by A, B and C respectively to complete the job.

A(24, 12, 8) ✓ Correct

B(12, 8, 24)

C(8, 12, 24)

D(8, 16, 24)

Correct answer: (A) (24, 12, 8)

Explanation

The times are 24, 12 and 8 hours for A, B and C.

A takes twice B's time and thrice C's time, so if A takes t, B takes t/2 and C takes t/3.

Rates: A = 1/t, B = 2/t, C = 3/t.

Together: (1 + 2 + 3)/t = 6/t = 1/4, so t = 24.

Then B = 24/2 = 12 and C = 24/3 = 8.

Method: add the individual rates to the combined rate.

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