Working together, A, B and C can do a certain work in 10 days. A is 20% more efficient than B, and C is 50% less than efficient than B, B alone can complete the same work in:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 27 days.
A, B, and C completed work in 10 days.
A is 20% more efficient than B, and C is 50% less efficient than B.
Total work = Efficiency of the workers × Time taken by them
Let the efficiency of B be 100x.
The efficiency of A = 100x + 100x × 20% = 120x
The efficiency of C = 100x - 100x × 50% = 50x
Effective efficiency of all three = 120x + 100x + 50x = 270x
Total work = 270x × 10 = 2700x
Now, B can do the work = 2700x/100x = 27 days