A train covers a distance of 360 km at a uniform speed. If the speed had been 10 km/h more, it would have taken 3 hours less for the same journey. What is the original speed of the train? MCQ with Answer and Explanation
A train covers a distance of 360 km at a uniform speed. If the speed had been 10 km/h more, it would have taken 3 hours less for the same journey. What is the original speed of the train?
A. 25 km/h
B. 40 km/h
C. 35 km/h
D. 30 km/h
Answer: Option D
Solution (By JKSSB Mock Tests)
Let original speed be s. 360/s - 360/(s+10) = 3. Dividing by 3: 120/s - 120/(s+10) = 1. 120(s + 10 - s) = s(s + 10) => 1200 = s(s + 10). Solving s^2 + 10s - 1200 = 0 gives (s-30)(s+40) = 0. Since speed is positive, s = 30 km/h.
Two express trains 220 meters and 180 meters long are tracking parallel in identical directions at speeds of 90 km/h and 72 km/h. Find the duration to pass each other.
Explanation:
New speed = 7/9 of usual speed => New time = 9/7 of usual time. Difference = 2/7 of usual time = 20 minutes. Therefore, 1/7 of usual time = 10 minutes => Usual time = 70 minutes.
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