A person walks from home to school at 4 km/h and arrives 5 minutes late. If he runs at 5 km/h, he arrives 4 minutes early. Find the distance. 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 C
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 motorboat rows 30 km downstream in 3 hours and tracks the identical route upstream back to the jetty point in 6 hours. Find the net speed index of the current stream flow.
Correct Answer: Option C
Explanation:
Downstream speed = 30 / 3 = 10 km/h. Upstream speed = 30 / 6 = 5 km/h. Speed of current stream flow = (10 - 5) / 2 = 5 / 2 = 2.5 km/h.
Downstream speed = 30 / 3 = 10 km/h. Upstream speed = 30 / 6 = 5 km/h. Speed of current stream flow = (10 - 5) / 2 = 5 / 2 = 2.5 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #3
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A cyclist covers a 1500-meter course in 5 minutes. Find his speed in km/h.
Correct Answer: Option C
Explanation:
Time = 5 minutes = 300 seconds. Speed = 1500 / 300 = 5 m/s. Converting to km/h = 5 * (18/5) = 18 km/h.
Time = 5 minutes = 300 seconds. Speed = 1500 / 300 = 5 m/s. Converting to km/h = 5 * (18/5) = 18 km/h.
This question belongs to:
Maths
Time Speed and Distance
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