Question
A car covers a distance of 450 km at a constant speed.
If the car’s speed had been 15 km/h faster, it would have taken 1 hour less to cover the same distance. What is the original speed of the car?Solution
Let the original speed of the car be x km/h. Time taken = 450/x. With the new speed (x + 15), time taken = 450/(x + 15). According to the question: 450/x − 450/(x + 15) = 1. Solving this: 450(x + 15 − x) = x(x + 15). 450 × 15 = x² + 15x. x² + 15x − 6750 = 0. Solving for x, we get x = 75 km/h. Thus, the original speed is 75 km/h Ans. d
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