1.  A does 20 % less work then B. If A can complete a piece of work in 7h, then B can do it in:
A. 4 h
B. 6 h
C. 8 h
D. 10 h

Answer: Option B

Explanation:

Let time taken by B = N

Efficiency ∝ 1/Time taken

So, if B is 100% efficient, then A is 80% efficient.

So, 80/100 = N /(15/2)

∴ N = 6 h