The speeds of a local and an express are in the ratio 3 : 5, and on a 300 km route the express takes 2 hours less. How long does the 200 m express take to overtake the 160 m local on a parallel line?

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Accepted Answer

32.4 s. Speeds 3k, 5k: 300/3k-300/5k=40/k=2 → k=20: 60 and 100 km/h. Relative =40 km/h =100/9 m/s. Time =360÷100/9=32.4 s. (8.1 s adds the speeds.)

The speeds of a local and an express are in the ratio 3 : 5, and on a 300 km route the express takes 2 hours less. How long does the 200 m express take to overtake the 160 m local on a parallel line?

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