A is 30% more efficient than B. How much time will they working together take to complete a job which A alone could have done in 23 days? Choose the correct choice from the following answers.
A) 11	B) 13	C) 20 3 / 17	D) 14	E) none of these

Rationale: explanation : ratio of times taken by a and b = 100 : 130 = 10 : 13 suppose b takes x days to work the 10 : 13 : : 23 : x = > x = 23 x 13 / 10 = 299 / 10 a ’ s one day work = 1 / 23 and b ’ s is 10 / 299 then a + b ‘ s work = 1 / 23 + 10 / 299 = 23 / 299 = 1 / 13 = > 13 days answer : option b
Answer: B