Question

An aeroplane flies from A to B 1080 km apart at a speed of 720 km per hour another aeroplane flies the same distance in 15 minutes less time at what speed does the plane fly

Answer 1

Time taken by the first plane = Distance/Speed = 1080/720 = 1.5 hours

The second plane takes 15 minutes less

15 minutes =  15/60 = 0.25 hours

Time taken by the 2nd plane = 1.5 - 0.25 = 1.25 hours

The speed of the 2nd plane = Distance/Time = 1080/1.25 = 864km/h

Answer 2

According to question

Distance    x = 1080 Km
Speed       v = 720 Km/ hour

thus time taken by the aeroplane be  t = x/v = 1080 / 720 = 1.5 hr

time taken by another    t' = t - 15 min = 1 hr 15 min = 1.25 hr
thus
  
speed of another plane = x / t' = 1080 / 1.25 = 864 km/hr