Question

An aeroplane takes 1 hour less for a journey of 1200km if its speed is increased by 100 km/hr from its usual speed of the plane.

Answer 1

Let the usual speed of plane be x km/hr,

Then the increased speed of the plane is = (x + 100) km/hr

Time taken by the plane under usual speed to cover 1200km = hr

Time taken by the plane under increased speed to cover 1200 km = hr

Therefore,

Since, the speed of the aeroplane can never be negative

Hence, the usual speed of aeroplane is 300 km/hr