一道比较绕的数学题
一个人从桥上跳下去逆流游泳.同时,在桥上的另一个人的帽子被吹落了下来顺着河流流走.跳下去游泳的那个人逆流游了10分钟后,向反方向游泳,他游泳直到拿到帽子为止.在距离桥1000米的地方,他拿到了帽子.求河流的速度
英文原文
Amanjumpsoffabridgeintoariverandbeginstoswimagainstthecurrent.Atthesamemomentahatblowsoffanotherman’sheadonthebridgeandbeginstofloatdownstream.After10minutestheswimmerturnsback,reachesthebridgeandcontinuestoswimonuntilhecatchesupwiththehat,whichhappens1,000metersfromthebridge.Theswimmerdoesnotvaryhiseffort.Whatisthespeedofthecurrent?