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The first volume of grade four is a math problem about trains.
A train is 200 meters long and travels at a speed of 60 meters per second. How long does it take to cross a 220-meter bridge?

Analytic analysis: (1) As shown on the right, students can find that the distance traveled by the train is: 200+220=420 (meters), so it takes 420 hours.

÷60=7 (seconds).

Consolidate a train with a length of 360 meters and a speed of 16 meters per second. It takes 90 seconds for the whole train to pass through a tunnel. How long is this tunnel?

It is known that the train speed is16m per second, and it takes 90 seconds for the whole train to pass through the tunnel. Time? The relationship between distances,

You can know the whole journey of the train. The whole journey is only the sum of the length of the train itself and the length of the tunnel, and you can find out the length of the tunnel. Train running for 90 seconds: 1690 1440 (m), tunnel length 1440360 1080 (m).

Consolidate the train with the length of150m and cross the 300m tunnel at the speed of18m per second. How long does it take for the train to cross the tunnel (enter the tunnel until it leaves completely)?

The analysis shows that the distance of the train passing through the tunnel is 300 150450 (m). Given the speed of the train, the time it takes for the train to pass through the tunnel.

That's 450 1825 (seconds).