A sedan covers a distance path of 480 km at a uniform tracking speed. If the speed index is lowered by 10 km/h, the trip records 2 hours longer. Find the original baseline speed. MCQ with Answer and Explanation
A sedan covers a distance path of 480 km at a uniform tracking speed. If the speed index is lowered by 10 km/h, the trip records 2 hours longer. Find the original baseline speed.
A. 45 km/h
B. 50 km/h
C. 55 km/h
D. 60 km/h
Answer: Option B
Solution (By JKSSB Mock Tests)
Let original speed be s. 480 / (s - 10) - 480 / s = 2 => 240 / (s - 10) - 240 / s = 1 => 2400 = s(s - 10). Solving s^2 - 10s - 2400 = 0 gives (s - 50)(s + 40) = 0. Baseline speed = 50 km/h.
A train 200 meters long passes a running man in 10 seconds when both move in the same direction. If the speed of the man is 6 km/h, find the speed of the train.
Explanation:
Relative speed = 200 / 10 = 20 m/s = 20 * (18/5) = 72 km/h. In the same direction, Relative Speed = Speed of train - Speed of man => 72 = Speed of train - 6 => Speed of train = 78 km/h.
A cross-country runner covers the sides of an equilateral triangular course at speeds of 8 km/h, 12 km/h and 24 km/h respectively. Find his average speed for the whole round.
Explanation:
Let each side of the triangular course be 24 km. Total perimeter = 3 * 24 = 72 km. Total time taken = 24/8 + 24/12 + 24/24 = 3 + 2 + 1 = 6 hours. Average speed = 72 / 6 = 12 km/h.
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