A and B can do a piece of work in 36 days, B and C can do a it in 60 days, A and C can do it in 45 days. C alone can do it in :

[A]90 days

[B]120 days

[C]150 days

[D]180 days

**180 days**

(A + B)’s 1 day’s work

(B + C)’s 1 day’s work

(C + A)’s 1 day’s work

On adding,

2(A + B + C)’s 1 day’s work

∴ (A + B + C)’s 1 day’s work

∴ c’s 1 day’s work

∴ C alone will complete the work in 180 days.

Hence option [D] is correct answer.