Question

A and B can do a piece of work in 10 days. B and C can do it in 12 days. A and C can do it in 15 days. How long will A take to do it alone?
A. 20 days
B. 24 days
C. 30 days
D. 40 days

Answer 1

Answer:

one day work of A and B=1/10 _______1

one day work of B and C=1/12 _______2

one day work of C and A=1/15 _______3

on adding eq 1 and 3

one day work of (A+B+C+A)=1/10+1/15

" " " " (2A+B+C) =3+2/30

" " " " " =5/30=1/6

put the value of eq 2 i.e one day work of B and C

one day work of 2A+1/12=1/6

" " " " 2A=1/6-1/12

" " " " 2A=2-1/12=1/12

one day work of A=1/(12×2)=1/24

work done by A=1÷1/24=24 days