Question

A and B together can do a piece of work in 30 days, B and C together can do it in 20 days, A starts the work and work on it for 5 days, then B takes up and work for 15 days. Finally C finishes the work in 18 days. The number of days in which C alone can do the work where doing it seperately is:

 (a) 120 days 

(b) 40 days 

(c) 60 days 

(d) 24 days

Answer 1

Correct option (d) 24 days

Explanation: 

According to the question

⇒A+B ………………….30 days 

⇒B+C…………………..20 days 

⇒A……………………...5 

B………………………5+10 

⇒C………………….10+8 days 

⇒Work done by (A+B) in 5 days = 2×5 = 10 work 

⇒Work done by (B+C) in 5 days = 10×3 = 30 work 

⇒Total work ……………………40 work 

⇒Remaining work = 60-40 = 20 work 

⇒Here we find that C does remaining 20 work in 8 days

⇒Therefore, time taken by C alone to complete the work