Question

A can do a piece of work in 4 days. B can do it in 5 days. With the assistanceof

C they completed the work in 2 days. Find in how many days can C alone do it?​

Answer 1

Answer:

20 days

Step-by-step explanation:

A can do a work alone in 4 days. And same work B can complete in 5 days. And with the help of C they can do the work in 2 days.

We dont know how much work is there to do. So lets find out that first..

Just take the LCM of 4,5 and 2 ….

You know from where 4,5 and 2 came. Its the time that A ,B and A+B+C took to complete the work.

LCM of 4,5 and 2 is 20.

So total work is 20. A took 4 days to complete 20 work alone i.e. it did 5 work per day.(efficiencyis 5 of A). B took 5 days to complete 20 work alone,with the efficiency of 4 per day.

Now the deciding factor A+B+C can do the work in 2 days means 10 work per day. A can do 5 work per day ,B can do 4 work per day.they both can do 9 work per day. As we know that

A+B+C can do 10 work a day.

And

A+B can do 9 work a day.

As A and B can do 9 work then what is left for C !

Only 1.

If C work with 1 work per day efficiency then how many days it will take to complete 20 work?

20 days.