A’s efficiency is 40% more than B’s efficiency. If A can do a piece of work in 15 hours, then in how many hours will B finish the same work ?
Answer & explanation
Correct answer: option 2
Time ∝ \(\frac{1}{efficiency}\)
A : B
Efficiency ⇒ 7 : 5
Time ⇒ 5 : 7
ATQ,
A's time ⇒ 5R = 15 ⇒ 1R = 3,
So, B's time ⇒ 7R = 7 × 3 = 21 hrs.