Multiple choice

A train travelling at a uniform speed for 360 Km would have taken 48 minutes less to travel the same distance if its speed were 5 Km/h more. Find the original speed of the train.

  1. 40 Km/h

  2. 45 Km/h

  3. 48 Km/h

  4. 50 Km/h
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let original speed be v. Time taken = 360/v. New time = 360/(v+5). Difference is 48 minutes (0.8 hours). 360/v - 360/(v+5) = 0.8. Solving this quadratic equation gives v = 45 km/h.

AI explanation

Using the formula Time = Distance / Speed, the original time is 360 / x and the faster time is 360 / (x + 5). The difference is 48 minutes, which is 48 / 60 or 4 / 5 of an hour, so 360 / x - 360 / (x + 5) = 4 / 5. Multiplying by 5x(x + 5) gives 1800(x + 5) - 1800x = 4x^2 + 20x, which simplifies to 9000 = 4x^2 + 20x. Dividing by 4 yields x^2 + 5x - 2250 = 0, and factoring this gives x = 45. The original speed of the train is 45 Km/h.

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