A car covers three successive 5 km stretches at speeds of 10 km/h, 20 km/h and 30 km/h respectively. Find its average speed. MCQ with Answer and Explanation

Question

A car covers three successive 5 km stretches at speeds of 10 km/h, 20 km/h and 30 km/h respectively. Find its average speed.

A. 15.42 km/h

B. 16.36 km/h

C. 20.00 km/h

D. 18.00 km/h

Answer: Option B

Solution (By JKSSB Mock Tests)

Total distance = 3 * 5 = 15 km. Total time taken = 5/10 + 5/20 + 5/30 = 1/2 + 1/4 + 1/6 = (6 + 3 + 2) / 12 = 11/12 hours. Average speed = 15 / (11/12) = 180 / 11 = 16.36 km/h.

This question belongs to: Maths Time Speed and Distance

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Question #1

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Two cyclists start from the same place in opposite directions. One goes towards North at 18 km/h and the other goes South at 22 km/h. What is the distance between them after 30 minutes?

A. 20 km

B. 25 km

C. 30 km

D. 15 km

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Correct Answer: Option A

Explanation:
Relative speed in opposite directions = 18 + 22 = 40 km/h. Time = 30 minutes = 0.5 hours. Distance = 40 * 0.5 = 20 km.

This question belongs to: Maths Time Speed and Distance

Question #2

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A cyclist covers a 3.6 km track in 12 minutes. Find his speed in meters per second.

A. 6 m/s

B. 4 m/s

C. 5 m/s

D. 8 m/s

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Correct Answer: Option C

Explanation:
Distance = 3.6 km = 3600 meters. Time = 12 minutes = 720 seconds. Speed = 3600 / 720 = 5 m/s.

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Question #3

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Two locomotive train units 140 meters and 110 meters long are running along parallel track loops in identical directions at speeds of 52 km/h and 42 km/h respectively. In what timeframe will the faster train clear the slower train completely?

A. 100 seconds

B. 110 seconds

C. 80 seconds

D. 90 seconds

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Correct Answer: Option D

Explanation:
Total path distance = 140 + 110 = 250 meters. Relative speed index in same direction = 52 - 42 = 10 km/h = 10 * (5/18) = 25/9 m/s. Time required = 250 / (25/9) = 250 * 9 / 25 = 10 * 9 = 90 seconds.

This question belongs to: Maths Time Speed and Distance

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