Be serious
badminton
2010-07-15 08:46:51
( reads)
1. Sister Feng is 40+20+30 = 90 meters away from me.
2. Sister Feng is walking at a speed of (20+10)m/min = 30m/min relative to me.
3. It will take 90 m/(30m/min) = 3 min for Sister Feng to crash with me.
4. Sister Feng moved 20m/min * 3min = 60 m at the end of the bridge
5. I moved 10m/min * 3min = 30 m at the beginning of the bridge.
6. I will not meet Sister Feng on the bridge. But I will meet her at the west end of the bridge. I could let her come down first. (xian1xia4hou4shang4).