Question

A can do a piece of work in 5 days, B in 4 days and A,B and C in 2 days, what is the time needed by C to complete the job ?

a) 20 days
b) 40 days
c) 30 days
d) 10 days
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Answer 1

Step-by-step explanation:

A can do 1/5 of work in 1 day

B can do 1/4 of work in 1 day

A+B+C can do 1/2 of work in 1 day

C= A+B+C -(A+B)

=1/2-(1/5+1/4)

=1/2-(9/20)= 1/20

C does 1/20 part of work in 1 day

C does whole work in 20 days