With an average speed of 50 km/h, a train reaches a destination in time. If it…
2021
With an average speed of 50 km/h, a train reaches a destination in time. If it goes with an average speed of 40 km/h, it is late by 30 minutes to reach its destination. What is the length of the total journey?
Answer: B. 100 km — Let the scheduled time be t hours and the journey length be d km. At 50 km/h, the train arrives on time: d = 50t. At 40 km/h, it is late by 30 minutes (0.5…
- A.
90 km
- B.
100 km
- C.
105 km
- D.
110 km
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Correct answer: B
Let the scheduled time be t hours and the journey length be d km. At 50 km/h, the train arrives on time: d = 50t. At 40 km/h, it is late by 30 minutes (0.5 hours): d = 40(t + 0.5). Equating the distances: 50t = 40(t + 0.5). Solving for t gives 10t = 20, so t = 2 hours. Substituting back into the first equation: d = 50 × 2 = 100 km.