Question 55

A train covers 360 km at a uniform speed. If the speed had been 10 km/h more,it would have taken 3 hours less for the same journey. What is the speed ofthe train (in km/h)?

Solution

Let the speed be x km/hr.

Total time taken = $$\frac{360}{x}$$ hour

if speed increased by 10 km/hr more , speed becomes, (x+10) kmph

Time becomes = $$\frac{360}{x+10}$$ hour

according to the problem,

$$\frac{360}{x}$$ hour - $$\frac{360}{x+10}$$ = 3

=> $$x^2 +10x - 1200=0$$

By solving we get, x = 30, -40. Hence 30 is our required answer.

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