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Question

A train covers a distance of 90 km at a uniform speed. Had the speed been 15 km/hour more, it would have taken 30 minutes less for the journey. The original speed of the train is ----- km/hr.

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Solution

Let original speed =xkm/hr

Time taken to travel =90xhr

New speed =(x+15)km/hr

Time taken to travel =90x+15hr

90x=90x+15+12

90x90x+15=12

90(1x1x+15)=12

x+15xx(x+15)=1180

15×180=x(x+15)

2700=x2+15x

x2+15x2700=0

x2+60x45x2700=0

x(x+60)45(x+60)=0

(x+60)(x45)=0

Speed can not be negative.

The original speed of the train is 45km/hr

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