A car traveling at a uniform speed covers 240 km. If the speed had been 10 km/h more, it would have taken 1 hour less. Find the initial speed. MCQ with Answer and Explanation
A car traveling at a uniform speed covers 240 km. If the speed had been 10 km/h more, it would have taken 1 hour less. Find the initial speed.
A. 40 km/h
B. 35 km/h
C. 50 km/h
D. 45 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let original speed be s. 240 / s - 240 / (s + 10) = 1 => 240(10) = s(s + 10) => 2400 = s(s + 10). Solving s^2 + 10s - 2400 = 0 gives (s - 40)(s + 50) = 0. Since speed is positive, s = 40 km/h.
A man covers 2/3 of a journey at 40 km/h, 1/4 of the journey at 30 km/h and the remainder at 10 km/h. What is his average speed for the entire journey?
Explanation:
Let the total distance be 120 km. First part = (2/3) * 120 = 80 km; Time = 80 / 40 = 2 hours. Second part = (1/4) * 120 = 30 km; Time = 30 / 30 = 1 hour. Remainder = 120 - 80 - 30 = 10 km; Time = 10 / 10 = 1 hour. Total time = 2 + 1 + 1 = 4 hours. Average speed = 120 / 4 = 32 km/h.
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