2 pipes X and Y fill a tub in 10 min and 15 min resp. Both are opened and at the end of 5 minutes X is turned off. How much time will the tub take to fill?

10 men working for 20 days, 5 hours a day can build a fence of length 20 meters. I need to build a fence of length 100 metres in 5 days and the men are willing to work 10 hours a day. How many men do we need?

If santa can walk a certain distance in 200 days when he rests 18 hours each day; how long will it take to walk twice the distance twice as fast and the rest half as long each day ?