Correct Answer - Option 3 : 150 days
Given:
A is twice efficient as of B and B is thrice efficient as of C.
Time taken to complete the whole work = 15 days
Formula used:
Efficiency = Total work/TIme
Calculation:
Efficiency of A and B = 2 : 1 ----(1)
Efficiency of B and C = 3 : 1 ----(2)
Eq. (1) × 3 and Eq. (2) × 1; then solve:
⇒ Efficiency of A : B : C = 6 : 3 : 1
Total efficiency = 6 + 3 + 1 = 10 units/day
⇒ Total work = 15 days × 10 units/day
⇒ Total work = 150 units
Time taken by C to complete the whole work = 150/1 = 150 days
∴ C complete the whole work in 150 days.