Mary can do a piece of work in 12 days. Rosy is 50% more efficient than Mary. The number of days taken by Rosy to do the same piece of work is? Choose the correct answer:
A) 7
B) 8
C) 9
D) 11
E) 10

Rationale: ratio of times taken by mary and rosy = 150 : 100 = 3 : 2 suppose rosy takes x days to do the work . 3 : 2 : : 12 : x = > x = 8 days . hence , rosy takes 8 days to complete the work . answer : b
Answer: B