Possible answers

來源: 於 2010-01-26 18:00:48 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

1. Purchase 28 cups of coffee, trade for 7 cups, totalling 35. Then get one more by trading in 4 of the 7 cups to get 36.

2. 1+2 go across: +2 min
1 goes back: +1 min
5+10 go across: +10 min
2 goes back: +2 min
1+2 go across: +2 min
17 minutes