A man covers 1/3 of his total journey at 30 km/h and the remaining 2/3 at 60 km/h. Find his average speed for the entire journey. MCQ with Answer and Explanation
A man covers 1/3 of his total journey at 30 km/h and the remaining 2/3 at 60 km/h. Find his average speed for the entire journey.
A. 48 km/h
B. 50 km/h
C. 45 km/h
D. 52 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let total distance be 90 km. First part = 30 km; Time = 30 / 30 = 1 hour. Remaining part = 60 km; Time = 60 / 60 = 1 hour. Total distance = 90 km, Total time = 2 hours. Average speed = 90 / 2 = 45 km/h.
A cyclist tracks a sector distance of 24 km at a certain speed. If he drops his pace by 2 km/h, he takes 1 hour more to cover the route. Find his baseline speed.
Explanation:
Let original speed be s. 24 / (s - 2) - 24 / s = 1 => 24(2) = s(s - 2) => 48 = s(s - 2). Solving s^2 - 2s - 48 = 0 yields (s - 8)(s + 6) = 0. Since speed must be positive, s = 8 km/h.
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