A takes 84 hours to finish the work. B completes the same work in one-fourth of the time taken by A. What fraction of the work will they complete in 12 hours?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. .
Time taken by A = 84 hours
Time taken by B = = 21 hours
LCM(84, 21) = 84
The efficiency of A = 84/21 = 4 units
The efficiency of B = 84/84= 1 unit
Work done by both in 12 hours = 12 × (4 + 1) = 12 × 5 = 60 units
Required fraction = =