A is thrice as efficient as B and is, therefore, able to finish a piece of work 10 days earlier than B. In how many days A and B will finish it together?  Choose the correct answer.
A) 3 1/2 days B) 3 4/5 days C) 3 days D) 5 days E) None of these
Explanation:   WC = 3:1   WT = 1:3   x 3x   1/x â€“ 1/3x = 1/10   x = 20/3   3/20 + 1/20 = 1/5 =&gt; 5 days   ANSWER IS 5 days
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A is thrice as efficient as B and is, therefore, able to finish a piece of work 10 days earlier than B. In how many days A and B will finish it together?