Q) A is thrice as good as workman as B and therefore is able to finish a job in 60 days less than B. Working together, they can do it in:

a) 20 days              b) 22 1/2 days               c) 25 days                     d) 30 days

Ans:

Given that, ratio of efficiencies A: B :: X:3X

Therefore, difference of A & B = 3X – X

Since given that difference of time taken = 60

=> 2x = 60 => X = 30

A alone does the work in X = 30 days,

B alone does the work in 3X = 90 days

A’s 1 day’s work = 1/30;

B’s 1 day’s work = 1/60

∴ (A + B)’s 1 day’s work = 1/30 + 1/90 = 4/90 = 2/45

∴ (A + B) together can finish the work in 1/(2/45) = 45/2 = 22 1/2 days

Hence, Answer is [B].

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