A train passes man A, walking along the line in its direction at 2 km/h, in 9 seconds. Its engine reaches man B, walking towards it at 4 km/h, exactly 30 minutes after reaching A, and passes B in 7 seconds. How long after the engine reaches B do A and B meet?

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Accepted Answer

1 h 45 min. Length: 9(v-5/9)=7(v+10/9) → v=115/18 m/s = 23 km/h. In 30 min the engine runs 11.5 km while A walks 1 km, so A is 10.5 km from B. Closing at 2+4=6 km/h → 1.75 h = 1 h 45 min.

A train passes man A, walking along the line in its direction at 2 km/h, in 9 seconds. Its engine reaches man B, walking towards it at 4 km/h, exactly 30 minutes after reaching A, and passes B in 7 seconds. How long after the engine reaches B do A and B meet?

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