A and B can complete a piece of work in 80 and 120 days respectively. They together start the work but A left after 20 days. After another… — Answer & Discussion

A and B can complete a piece of work in 80 and 120 days respectively. They together start the work but A left after 20 days. After another 12 days C joined B and now they complete the work in 28 more days. In how many days C can complete the work, working alone?

A100 days
B112 days
C120 days
D126 days

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Discussion 1

CCommunity20 May 2019

Solution
A did the work for 20 days, B did the work for (20 + 12 + 38) = 60 days, C did the work for 28 days.
Let C alone can complete the work in x days.

Fraction of work did by A + Fraction of work did by B + Fraction of work did by C = 1

Or 20/80+60/120+28/x=1

Or x=28×4 = 112 days

C alone can complete the work in 112 days