Q. 454.1( 65 Votes )

A train covers a distance of 480 km at a uniform speed. If the speed had been 8 km/hr less then it would have taken 3 hours more to cover the same distance. Find the usual speed of the train.

Answer :

Let the usual speed of the train be x km/h

Reduced speed of the train = (x – 8) km/h


Distance of journey = 480km


Time taken to reach destination at usual speed =


Time taken to reach destination at reduced speed =


According to given question


 ⇒ 

⇒ 

⇒ 

⇒ x2 – 8x = 1280

⇒ x2 – 8x – 1280 = 0

⇒ x2 – 40x + 32x – 1280 = 0

⇒ x(x – 40) + 32(x – 40) = 0

⇒ (x – 40)(x + 32) = 0

⇒ x = 40 or x = – 32

⇒ x = 40 (speed cannot be negative)


Hence the usual speed of the train is 40 km/h

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