Shrenik switched on a bulb at 2 : 39 : 40 hours and switched it off on the same day at 12 : 30 : 34 hours. For how long was the bulb in switched-on mode?
A boy walking at the speed of 4 km/hr covers a certain distance in 6 hours 15 minutes. If he covers the same distance by cycle in 5 hours, then what is the speed (in km/hr) of the cycle?