The ratio of the speeds of two trains is 7 : 8. If the second train travels…
2025
The ratio of the speeds of two trains is 7 : 8. If the second train travels 400 km in 4 hours, what is the speed of the first train (in km/hr)?
Answer: B. 87.5 — Concept: Speed = Distance ÷ Time. When two speeds are given in a ratio (a : b) and one of the actual speeds is known, the other speed is found by setting up a…
- A.
80
- B.
87.5
- C.
92.5
- D.
98
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Show answer & explanation
Correct answer: B
Concept: Speed = Distance ÷ Time. When two speeds are given in a ratio (a : b) and one of the actual speeds is known, the other speed is found by setting up a proportion with the ratio and solving for the unknown.
Application:
Speed of the second train = Distance ÷ Time = 400 ÷ 4 = 100 km/hr.
Given ratio of speed of first train to second train = 7 : 8.
Let the speed of the first train = x km/hr. Then x / 100 = 7 / 8.
Solving: x = (7 × 100) / 8 = 700 / 8 = 87.5 km/hr.
Cross-check: 87.5 / 100 = 0.875 = 7/8, which matches the given ratio, confirming the result.