The speeds of two cars are in the ratio 5 : 3. If they cover the same total distance, and the slower car takes 2.5 hours, how much time does the faster car take? MCQ with Answer and Explanation
The speeds of two cars are in the ratio 5 : 3. If they cover the same total distance, and the slower car takes 2.5 hours, how much time does the faster car take?
A. 1.5 hours
B. 1.2 hours
C. 2.0 hours
D. 1.8 hours
Answer: Option A
Solution (By JKSSB Mock Tests)
Ratio of speeds = 5:3, so ratio of times taken = 3:5. The slower car corresponds to 5 parts = 2.5 hours => 1 part = 0.5 hours. Time for the faster car = 3 parts = 3 * 0.5 = 1.5 hours.
Explanation:
Let original speed be s. 180 / (s - 5) - 180 / s = 1 => 180(5) = s(s - 5) => 900 = s(s - 5). Solving s^2 - 5s - 900 = 0 gives (s - 30)(s + 25) = 0. Since speed is positive, s = 30 km/h.
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