8. A, B and C can do a work in 12, 15 and 20 days respectively. They started working together but
4 days A left. In how many days will B and C complete the work?
Answers
Answer:
Step-by-step explanation:
In one day,
A can do - 1/12 part of work
B can do - 1/15 part of work
C can do - 1/20 part of work
A, B and C can together do 1/12 + 1/15 + 1/20 = 5 + 4 + 3 / 60 = 12/60 = 1/5
So A, B and C can together complete the work in 5 days.
First let us find how much time B and C together take to do the work.
B & C can together do 1/15 + 1/20 = 4+ 3/ 60 = 7/60 in one day
=> B & C can together do the work in 60/7 days.
Given, A, B and C worked together for 4 days and then A left.
Work done by A, B and C in 4 days before A left = 4/5 part of work.
Work left to be completed by B & C together = 1 - 4/5 = 1/5 part.
Time taken by B & C to complete whole work = 60/7 days.
Time taken by B& C to complete 1/5th part of work = 1/5 * 60/7 = 12/7 days