Question

A and B can do a piece of work in 72 days: B and C can do it in 120 days: A and C can
do it in 90 days in what time can A alone do it?
A) 80days
B) 100 days
C) 120 days
D) 150 days​

Answer 1

Answer:

option B

Explanation:

According to question,

(A + B)’s one day’s work = \frac{1}{72}

(B + C)’s one day’s work = \frac{1}{120}

and (C + A)’s one day’s work = \frac{1}{90}

On adding all three,

2 (A + B + C)’s one day’s work = \frac{1}{72}+ \frac{1}{120}+ \frac{1}{90}

= \frac{5+3+4}{360} = \frac{1}{30}

∴ (A + B + C)’s one day’s work = \frac{1}{60}

∴ A, B and C together can finish the whole work in 60 days.

Hence option [B] is the right answer