The platform of a station 400 m long starts exactly where the last span of a bridge 1.2 km long ends. How long will a train 200 m long and travelling at the speed of 72 km/htake to cover the distance between the starting point of the span of the bridge and the far end of the platform ?
The average age of fifteen persons is 32 years. If two more persons are added, then the average is increased by 3 years. The new persons have age difference of 7 years. The age (in years) of the younger among the new persons is: