A scooter travels from town P to town Q at 30 km/h and returns at 45 km/h. Find the net average speed for the round journey. MCQ with Answer and Explanation
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Question #1
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An aeroplane flies along the four sides of a square at speeds of 200, 400, 600 and 800 km/h. Find the average speed of the plane around the field.
Correct Answer: Option D
Explanation:
Let each side of square be 2400 km (LCM of 200, 400, 600, 800). Total distance = 4 * 2400 = 9600 km. Total time = 2400/200 + 2400/400 + 2400/600 + 2400/800 = 12 + 6 + 4 + 3 = 25 hours. Average speed = 9600 / 25 = 384 km/h.
Let each side of square be 2400 km (LCM of 200, 400, 600, 800). Total distance = 4 * 2400 = 9600 km. Total time = 2400/200 + 2400/400 + 2400/600 + 2400/800 = 12 + 6 + 4 + 3 = 25 hours. Average speed = 9600 / 25 = 384 km/h.
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Maths
Time Speed and Distance
Question #2
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A professional athlete tracks a loop of radius 140 meters in 88 seconds. What is his speed in km/h?
Correct Answer: Option A
Explanation:
Circumference of loop = 2 * (22/7) * 140 = 880 meters. Speed = 880 / 88 = 10 m/s. Converting to km/h = 10 * (18/5) = 36 km/h.
Circumference of loop = 2 * (22/7) * 140 = 880 meters. Speed = 880 / 88 = 10 m/s. Converting to km/h = 10 * (18/5) = 36 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #3
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A train running at 72 km/h overtakes a cyclist riding at 12 km/h in the same direction in 12 seconds. Find the length of the train.
Correct Answer: Option A
Explanation:
Relative speed = 72 - 12 = 60 km/h = 60 * (5/18) = 50/3 m/s. Length of train = Relative speed * Time = (50/3) * 12 = 200 meters.
Relative speed = 72 - 12 = 60 km/h = 60 * (5/18) = 50/3 m/s. Length of train = Relative speed * Time = (50/3) * 12 = 200 meters.
This question belongs to:
Maths
Time Speed and Distance
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