Question

a car travels 200km usaly and if it travels 1hr less for same distance and speed of car increases by 100km/hr than find its usal speed

Answer 1

Let the usual speed of car = x km / h

Time taken to cover distance 200 km by a car = Distance / Speed = 200 / x

Time taken to cover distance 200 km by a car if its speed increase by 100 km / h

= 200 / x + 100

According to question

200 / x = 200 / x + 100 + 1

200 / x - 200 / x + 100 = 1

200 ( x + 100) - 200(x) / x ( x + 100) = 1

200x - 200x +20000 / x² + 100 x = 1

x² + 100 x - 20000 = 0

x² + (500 - 400)x - 20000 = 0

x² + 500x - 400x - 20000 = 0

x(x + 500) - 400(x + 500) = 0

(x - 400) (x + 500) = 0

x = 400 or x = (-500)

Speed can't be negative, So

The usual speed of car is 400 km /h.

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