问题描述：
英语翻译
it takes a ship 16 hours sailing downstream 120km and upstream 80 km,it also takes the ship 16 hours sailing downstream 60km and upstream 120 km.what is the speed of the stream?
it takes a ship 16 hours sailing downstream 120km and upstream 80 km,it also takes the ship 16 hours sailing downstream 60km and upstream 120 km.what is the speed of the stream?
问题解答：
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