A car covers a distance of 180 km at 45 km/h and another 180 km at 60 km/h. Find the total time spent during the journey. MCQ with Answer and Explanation
A worker handles a total factory delivery run of 160 km. He maps the first 60 km section at 30 km/h and the final 100 km segment section at 50 km/h. Find the mean average speed recorded across the full delivery run.
Explanation:
Total distance = 160 km. Time for section 1 = 60 / 30 = 2 hours. Time for section 2 = 100 / 50 = 2 hours. Total duration time = 4 hours. Average speed across run = 160 / 4 = 40 km/h.
A boat goes 6 km upstream and returns back to the starting point in 2 hours. If the speed of the stream is 4 km/h, find the speed of the boat in still water.
Explanation:
Let speed of boat in still water be v. 6 / (v - 4) + 6 / (v + 4) = 2 => 3 / (v - 4) + 3 / (v + 4) = 1 => 3(v + 4 + v - 4) = v^2 - 16 => 6v = v^2 - 16 => v^2 - 6v - 16 = 0. Solving the quadratic equation gives (v - 8)(v + 2) = 0. Since speed must be positive, v = 8 km/h.
A train passes a pedestrian standing on a platform in 8 seconds and passes the platform itself, which is 200 meters long, in 18 seconds. Find the speed of the train in km/h.
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