Question

An aero-plane takes 1 hr less for a journey of 1200 km. If its speed is increased by 60 km/hr from the initial speed. Find the initial speed of the plane.

Answer 1

Let the time taken by the plane to cover 1200 km be t₁, when the initial speed of the plane is v km/h.

Let the time taken by the plane to cover 1200 km be t₂, when the speed of the plane is (v + 60) km/h.

∴and

It is given that t₁ – t₂ = 1.

Since the speed cannot be negative,

Hence, the initial speed of the plane is.