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 much time will A alone take to finish the work?

A and B can do a piece of work in = 12 days

Work done by A and B in 1 day =

B and C can do a piece of work in = 15 days

Work done by C and B in 1 day =

A and c can do a piece of work in = 20 days

Work done by A and C in 1 day =

Now adding, we get,

2(A+B+C)^’s 1 day work =

A+B+C one day work =

∵ A’s 1 day work = (A+B+C)’s 1 day work – ( B+C)’s 1 day work

=

∴ A can finish the work in =