A and B can do a piece of work in 72 days; B and C can do it in 120 da

Question

A and B can do a piece of work in 72 days; B and C can do it in 120 days; A and C can do it in 90 days. In what time can A alone do it ?

(A) 150 days
(B) 120 days
(C) 100 days
(D) 80 days
(E) 70 days

imeanup · Answer

Ans B

Attach Screenshot

Geet03 · Answer

Can you please explain how are we calculating efficiency?

igoaid · Answer

1/A + 1/B = 1/72 ----- (i)
1/B + 1/C = 1/120 ---- (ii)
Subtracting (i) and (ii)
1/A - 1/C = 1/180 ---- (iii)
1/A + 1/C = 1/90 ---- (iv)
Adding (iii) and (iv)
2/A = (1+2)/180 = 3/180 = 1/60
2/A = 1/60
1/A = 120
A = 120

imeanup · Answer

The efficiency of an individual? It is mentioned to the right in the pic. Firstly, we are calculating the combined efficiency, then we are substituting the eff. of an individual.

Geet03

Let me share another pic with complete detail and please tag me for any further clarification

Posted from my mobile device

bumpbot · Answer

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A and B can do a piece of work in 72 days; B and C can do it in 120 da

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A and B can do a piece of work in 72 days; B and C can do it in 120 da

Prep Toolkit

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