a train travels 180km at a uniform speed. if the speed had been 9km/hr more it would have taken 1 hour less for the same journey. find the speed of the train. plz explain step wise.

Asked by Rutuja Mehta | 18th Jan, 2014, 07:35: PM

Expert Answer:

Let the speed of train be x km /h

Distance = 180 km

So, time =  180 / x

When speed is 9 km/h more, time taken = 180 / x+9 

According to the given information:

180 / x  -  180 / x+9 = 1

180 (x+9-x) / x(x+9)  =  1

180 * 9 = x(x+9)

1620 = x2 + 9x 

x2 + 9x - 1620 = 0

x2 + 45x - 36x - 1620 = 0 

x(x+45) - 36(x+45) = 0

(x-36)(x+45) = 0

x = 36 or -45

But x being speed cannot be negative.

So, x = 36

Hence, the speed of the train is 36km/h.

Answered by  | 19th Jan, 2014, 04:57: PM

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