Pipes A, B and C can fill a tank in 30 h, 40 h and 60 h respectively. Pipes A, B and C are opened at 7 a.m., 8 a.m., and 10 a.m. respectively on the same day. When will the tank be full?
A train leaves Amritsar at 6 am & reaches Delhi at 12 noon. Another train leaves Delhi at 8 am & reaches Amritsar at 5 pm. At what time do the two trains cross each other?
From the top and bottom of a straight hill, the angle of depression and elevation of the top of a pillar of 10 m height are observed to be 60° and 30° respectively. The height (in metres) of the hill is