100

来源: 沙发 于 2015-12-29 13:28:12 [] [博客] [旧帖] [给我悄悄话] 阅读数 : (266 bytes)
本帖于 2015-12-29 13:41:31 时间, 由普通用户 沙发 编辑
回答: 这个好！小朋友们动动脑吧 由 crazydinosaur 于 2015-12-29 10:56:14

fake money is 0.

buyer +70 for shoes and +30 change, total net gain +100

seller. -70 for shoes and -30 to neighr when returns the 100 back. total loss 100

neighbor: -100 first  then +100. net change is 0

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