A is 30% more efficient than B .how much time they will working together take to complete a job which A alone could have done in 23 days?  Pick one:
A) 25 days
B) 13 days
C) 14 days
D) 20 days
E) 15 days

Rationale: "the ratio of times taken by a and b = 100 : 130 = 10 : 13 suppose b can do work in x days then 10 : 13 : : 23 : x x = ( 23 * 13 ) / 10 x = 299 / 10 a ' s 1 day ' s work = 1 / 23 b ' s 1 day ' s work = 10 / 299 ( a + b ) ' s 1 day ' s work = 1 / 23 + 10 / 299 = 23 / 299 = 1 / 13 a and b together can do work in 13 days answer ( b )"
Answer: B