A person runs along the sides of an equilateral triangular field at speeds of 10 km/h, 15 km/h and 30 km/h respectively. Find his average speed for the entire perimeter. MCQ with Answer and Explanation
A person runs along the sides of an equilateral triangular field at speeds of 10 km/h, 15 km/h and 30 km/h respectively. Find his average speed for the entire perimeter.
A. 15 km/h
B. 20 km/h
C. 12 km/h
D. 18 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let each side of the triangular field be 30 km (LCM of 10, 15, 30). Total distance = 3 * 30 = 90 km. Total time taken = 30/10 + 30/15 + 30/30 = 3 + 2 + 1 = 6 hours. Average speed = 90 / 6 = 15 km/h.
Explanation:
New speed = 7/8 of usual speed => New time = 8/7 of usual time. Difference = 1/7 of usual time = 10 minutes. Usual time = 10 * 7 = 70 minutes.
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.
Excluding operational station stops, a city bus routes at an average of 42 km/h, and including stops its net average speed is 35 km/h. For how many minutes does it stop per hour?
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