NIFT UG 2013 Question Paper with solutions

Question : 37 of 150

Marks: +1, -0

A and B can do a piece of work in 12 days, B and C can do it in 15 days and C and A can do the same work in 20 days. Find the number of days in which A alone can do the same work.

20 days
30 days
45 days
60 days

Validate

Solution:

(A + B)’s 1 day work

=1/2

(B + C)’s 1 day work

=1/5

(C + A)’s 1 day work

=1/20

2(A + B + C)’s 1 day work

=\;\;{1}/{12}+\;\;{1}/{15}+\;\;{1}/{20}=\;\;{5+4+3}/{60}=\;\;{1}/{5}

(A + B + C)’s 1 day work

=1/10

A’s 1 day work

=1/10-1/5={3-2}/30=1/30

So, A can do the same work in 30 days.

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