A is twice efficient as B and together they do the same work in as much time as C and D together. If C and D can complete the work in 20 and 30 daysrespectively, working alone ,then in how many days A can complete the work individually:	Choices.
A) 12 days  B) 18 days  C) 24 days  D) 30 days  E) None of these
Explanation:   A + 18 days = C + D   | | | |   Ratio of efficiency 10x + 5x 9x + 6x   |________| |_________|   15x 15x   Therefore , ratio of efficiency of A:C =10:9   Therefore, ratio of days taken by A:C = 9:10   Therefore, number of days taken by A = 18 days   Answer: 18 days
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A is twice efficient as B and together they do the same work in as much time as C and D together. If C and D can complete the work in 20 and 30 daysrespectively, working alone ,then in how many days A can complete the work individually: