A, B and C can finish a job working alone in 20, 30 and 60 days respectively. They all work together for 1 day, then A and B quit. How many days C working alone will take to finish the remaining part of the job?

A school has 8 periods of 45 minutes each, every day. How long will each period be if the school has to have 9 periods everyday, assuming the working hours to be the same?

A and B together can complete a work in 24 days. B alone does 1/3rd part ofthis work in 12 days. How many days will A alone take to complete the remaining work?

A and B together can do a piece of work in 36 days, B and C together can do it in 24 days. A and C together can do it in 18 days. The three working together can finish the work in

18 men or 36 boys working 6 hours a day can plough a field in 24 days. In how many days will 24 men and 24 boys working 9 hours a day plough the same field ?