Freight car (200+280) × 3/(5+3) ÷15 =12 (m)

2. Solution: Let the car be x meters long and y meters/second per hour.

( 1000+x)/y=60

( 1000-x)/y=40

The solution is y=20 x=200, and the train speed is 20 meters per second.

3. Solution: 40×1000/3600 =100/9 (m/s)

Head-on train speed:150 ÷ 6-100/9 =125/9 (m/s)

4. Solution: Let's meet for the first time in X minutes.

360x-240x=400

120x=400

X= 10/3 (minutes)

Answer: 360×10/3 ÷ 400 =1200 ÷ 400 = 3 (circle)

B: 240×10/3 ÷ 400 =1200 ÷ 400 = 2 (circle)