13.A and B together can do a work in 25days. They work to together for 15days and then B leaves.A finishes the rest of the work in `20` days.How many days would each take to complete the work seperately?

A is twice as efficient as B and together they finish a piece of work in 18 days. How many days will A take to complete the work alone?

Acan do a work in 6 days and B in 9 days. How many days will both take together to complete the work?

Vaibhav can do a piece of work in 60 days. He works there for 15 days and then Sandeep alone finishes the remaining work in 30 days. In how many days will Vaibhav and Sandeep working together finish the work?

A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :

A can do a piece of work in 20 days and B can do the same piece of work in 30 days. They start working together and work for 5 days and then both leave he work. C alone finishes the remaining work in 14 days. In how many days will C alone finish the whole work?