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A car covers a distance of 840 km at a uniform speed. If the speed of the car is 10 km/h more, then it takes 2 hours less to cover the same distance. Find the original speed of the car.

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by Valtea

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by Valtea

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now given the distance covered ny car is 840km.

therefore time taken by car = 840/x

now if speed becomes x+10

then time taken will be 8400/x+10

now according to the question

8400/x-8400/x+10=2

840(1/x - 1/x+10)=2

8400/x^2+10x=2

2x^2+20x-8400=0

x^2+10x-4200=0

solve this equation u will get the original speed

840/x-840/(x+10)=2

(420x+4200-420x)/x^2+10x=2

x^2+10x-4200=0

x^2+70x-60x-4200=0

(x+70)(x-60)=0

x=60 km/hr