Q54 of 68 Page 9

An aeroplane left 30 minutes later than its scheduled time; and in order to reach its destination 1500 km away in time, it has to increase its speed by 250 km/hour from its usual speed. Determine its usual speed.

Let the usual speed of the plane = x km/hr


Total distance = 1500km




Actual Speed of the plane = (x + 250) km/hr








⇒ x2 + 250x – 750000 = 0


⇒ x2 + 1000x – 750x – 750000 = 0


⇒ x(x + 1000) – 750(x + 1000) = 0


⇒ (x – 750) (x + 1000) = 0


⇒ x + 1000 = 0 or x – 750 = 0


⇒ x = - 1000 or x = 750


⇒ x = 750 [∵ speed can’t be negative]


Hence, the usual speed of the aeroplane was 750km/hr


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