If A, B and C can do a work in 6 days, 9 days and 11 days, respectively, then, working together, how many days will they take to do the work?

Sara can finish a work in 18 days and Tara can complete the same work in 15 days. Tara worked for 10 days and left the job. In how many days can Sara finish the remaining work alone?

40 men can complete a work in 30 days. However, if 10 men leave the group, how many days will the group take to complete the work?

A can finish a job in 8 hours and B can finish the same job in 12 hours independently. If they work simultaneously, in how many hours can they do the same job?