Q) A and B can do a job together in 7 days. A is 1 3/4 times as efficient as B. The same job can be done by A alone in :

a) 9 1/3 days              b) 11 days               c) 12 1/4 days                     d) 16 1/3 days

Ans:

Since A is 7/4 times as efficient as B, therefore A will do 7/4 times work of B.

B’s 1 day’s work = 1/B

A’s 1 day’s work = 7/4 x 1/B = 7/4B

(A + B)’s 1 day’s work = 1/B + 7/4B = 11/4B

Since Time taken by (A + B) to finish 11/4B work = 1 day

∴ Time taken by (A + B) to finish whole work = 1 /(11/4B) = 4B/11 days

By given condition, 4B/11 = 7

∴ B = 11 x 7 /4 = 77/4 days

∴ time taken by A = (77/4)/(7/4) = 11 days

Hence, Answer is [B].

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