A train passes a static observer in 8 seconds and a platform 120 meters long in 14 seconds. Find the length of the train. MCQ with Answer and Explanation
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Question #1
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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.
Correct Answer: Option A
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.
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.
This question belongs to:
Maths
Time Speed and Distance
Question #2
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A jogger runs along a square perimeter of side 45 meters. If his speed is 10.8 km/h, how much time does he take to finish one full round?
Correct Answer: Option B
Explanation:
Perimeter of the course = 4 * 45 = 180 meters. Speed = 10.8 km/h = 10.8 * (5/18) = 3 m/s. Time required = Distance / Speed = 180 / 3 = 60 seconds.
Perimeter of the course = 4 * 45 = 180 meters. Speed = 10.8 km/h = 10.8 * (5/18) = 3 m/s. Time required = Distance / Speed = 180 / 3 = 60 seconds.
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Maths
Time Speed and Distance
Question #3
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A man walks from his residence to a focal point at 4 km/h and arrives 10 minutes late. If he increases his speed to 5 km/h, he arrives 2 minutes early. Find the distance.
Correct Answer: Option B
Explanation:
Time difference = 10 - (-2) = 12 minutes = 12/60 = 0.2 hours. Let distance be d. d / 4 - d / 5 = 0.2 => d / 20 = 0.2 => d = 4 km.
Time difference = 10 - (-2) = 12 minutes = 12/60 = 0.2 hours. Let distance be d. d / 4 - d / 5 = 0.2 => d / 20 = 0.2 => d = 4 km.
This question belongs to:
Maths
Time Speed and Distance
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