1.  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?
A. 11 days
B. 13 days
C. 203/17 days
D. None of these

Answer: Option B

Explanation:

Ratio of times taken by A and B = 100 : 130 = 10 : 13.

Suppose B takes x days to do the work.

Then, 10 : 13 :: 23 : x

=>  x = ( 23 x 13 )   =>  x = 299 .
10 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 + 10 ) = 23 = 1 .
23 299 299 13

Therefore, A and B together can complete the work in 13 days.