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?	Select:	A) 11 days	B) 13 days	C) 20 3/17 days	D) 21 days	E) None of these
Explanation:   Ratio of times taken by A and B = 100:130 = 10:13   Suppose B takes x days to do the work.   x = (23 * 13)/10 = 299/10   A's 1 day work = 1/23; B's 1 day work = 10/299   (A + B)'s 1 day work = (1/23 + 10/299) = 1/13   A and B together can complete the job in 13 days.   ANSWER IS 13 days
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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?