A car covered a distance of 200 km at a uniform speed. If the speed is reduced by 10 km/h, the time taken increases by 1 hour. Find the original speed. MCQ with Answer and Explanation
A car covered a distance of 200 km at a uniform speed. If the speed is reduced by 10 km/h, the time taken increases by 1 hour. Find the original speed.
A. 60 km/h
B. 50 km/h
C. 45 km/h
D. 55 km/h
Answer: Option B
Solution (By JKSSB Mock Tests)
Let original speed be s. 200 / (s - 10) - 200 / s = 1 => 200(s - s + 10) = s(s - 10) => 2000 = s(s - 10). Solving s^2 - 10s - 2000 = 0 gives (s - 50)(s + 40) = 0. Since speed is positive, s = 50 km/h.
Explanation:
Distance for A to run = 500 - 140 = 360 meters. Ratio of speeds A:B = 3:4. Time taken by A to run 360m is proportional to 360 / 3 = 120 units. In the same time, B runs 4 * 120 = 480 meters. B needs 500m to win but only reaches 480m. Thus, A wins, and B is 500 - 480 = 20 meters behind. A wins by 20 meters.
If a student walks from his house to school at 5 km/h, he is late by 10 minutes. However, if he walks at 6 km/h, he is late by only 2 minutes. Find the distance between his house and school.
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