Question

If the speed of an aeroplane is decreased by 120 kilometre per hour it takes 18 minutes more to travel some distance if the speed is increased by 180 kilometre per hour it takes 18 minutes less to travel the same distance find the average speed of the aeroplane and the distance

Answer 1

Distance = xkm

x/120-18/60=x/180+18/60

multiply by 360

3x-108=2x+108

x = 216 Km.

distance =216 km

Time for onwardjourney=216/120 =

1.8 hrs

Time for backwardjourney=216/180

= 1.2 hrs

Average speed=216+216/1.8 +1.2=

432/3 = I44 km/hr