A motorboat registers a speed of 14 km/h in still water. If the river current tracks at 2 km/h, find the duration required to complete a 48 km downstream course. MCQ with Answer and Explanation
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Question #1
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Two trains of equal length cross a pole in 12 seconds and 18 seconds respectively. If the length of each train is 180 meters, find the time taken by them to pass each other when running in opposite directions.
Correct Answer: Option C
Explanation:
Speed of first train = 180 / 12 = 15 m/s. Speed of second train = 180 / 18 = 10 m/s. Total distance to cross = 180 + 180 = 360 meters. Relative speed in opposite directions = 15 + 10 = 25 m/s. Time taken = 360 / 25 = 14.4 seconds.
Speed of first train = 180 / 12 = 15 m/s. Speed of second train = 180 / 18 = 10 m/s. Total distance to cross = 180 + 180 = 360 meters. Relative speed in opposite directions = 15 + 10 = 25 m/s. Time taken = 360 / 25 = 14.4 seconds.
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Maths
Time Speed and Distance
Question #2
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A person leaves point A at 5:00 AM at 30 km/h. Another leaves A at 7:00 AM at 40 km/h in the same direction. At what distance from A will they meet?
Correct Answer: Option B
Explanation:
By 7:00 AM, the first person covers 30 * 2 = 60 km. Relative speed = 40 - 30 = 10 km/h. Time to meet = 60 / 10 = 6 hours. Distance from A = Speed of second person * Time = 40 * 6 = 240 km.
By 7:00 AM, the first person covers 30 * 2 = 60 km. Relative speed = 40 - 30 = 10 km/h. Time to meet = 60 / 10 = 6 hours. Distance from A = Speed of second person * Time = 40 * 6 = 240 km.
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Maths
Time Speed and Distance
Question #3
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A man can row 12 km/h in still water. He finds that it takes him twice as long to row upstream as to row downstream. Find the speed of the stream.
Correct Answer: Option D
Explanation:
Let stream speed be c. Upstream speed = 12 - c, Downstream speed = 12 + c. Given: 2 * (12 - c) = 12 + c => 24 - 2c = 12 + c => 3c = 12 => c = 4 km/h.
Let stream speed be c. Upstream speed = 12 - c, Downstream speed = 12 + c. Given: 2 * (12 - c) = 12 + c => 24 - 2c = 12 + c => 3c = 12 => c = 4 km/h.
This question belongs to:
Maths
Time Speed and Distance
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