R

A and B can do a piece of work in 12 days, B and C in 15 days, C and A in 20 days. How long A alone will take to do the work?

N

Nandan

(A+B)'s one day work is 1/12

(B+C)'s one day work is 1/15

(C+A)'s one day work is 1/20

Thus,2(A+B+C)'s one day work is 1/12+1/15+1/20=1/5

so,(A+B+C) can complete the work in 10 days.

(A+B+C)'s one day work=1/10

A 's one day work=1/10-1/15=1/30

So A can complete the work in 30 days

5