While boarding an aeroplane, a passenger got hurt. The pilot showing promptness and concern, made arrangements to hospitalise the injured and so the plane started late 30 minutes to reach the destination, 1500 km away in time, the pilot increased the speed by 100 km/hr. Find the original speed/hour of the plane.

Answer

500 km/hr

Explanation

Let the original speed of the plane be x km/hr. Then,
`(1500)/(x)-(1500)/((x+100))=(30)/(60)implies(1)/(x)-(1)/((x+100))=(1)/(3000)impliesx^(2)+100x-300000=0`
`impliesx^(2)+600x-500x-300000=0.`
His promptness is appreciable.