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A is twice as efficient as B. Working together they complete a work in 12 days. How many days would A alone take to complete the work?

Competition practiceTime & Work / Pipes

A20
B24
C36
D18

Step-by-Step Solution

Let B'

s

rate =

x

, A'

s = 2 x

. Together

3 x = 1/12

, so

x = 1/36

and A'

s

rate = 2/36 = 1/18. A alone takes 18 days.

Answer: D) 18

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