A car covered a distance of 300 km at a uniform speed. If the baseline speed is lowered by 10 km/h, the trip duration spikes by 1 hour. Find the original speed. MCQ with Answer and Explanation
A car covered a distance of 300 km at a uniform speed. If the baseline speed is lowered by 10 km/h, the trip duration spikes by 1 hour. Find the original speed.
A. 65 km/h
B. 70 km/h
C. 55 km/h
D. 60 km/h
Answer: Option D
Solution (By JKSSB Mock Tests)
Let original speed be s. 300 / (s - 10) - 300 / s = 1 => 300(10) = s(s - 10) => 3000 = s(s - 10). Solving s^2 - 10s - 3000 = 0 yields (s - 60)(s + 50) = 0. Since speed must be positive, s = 60 km/h.
Explanation:
New speed = 7/9 of usual speed => New time = 9/7 of usual time. Difference = 2/7 of usual time = 12 minutes. 1/7 of usual time = 6 minutes => Usual time = 42 minutes.
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