刚在猴哥难题112上看到一道题:
“Seven one-dollar bills are to be distributed among Lucia, Gomez, and Domingo so that each person receives at least $1. ”
问:Which is big?
A- The number of ways to distribute the bills so that at least one person receives at least $3.
B- The total number of ways to distribute the bills.
答案给的是C,没算明白它们怎么就equal了!
解答:
根据抽屉原理,把7块钱放在三个抽屉里,至少有一个抽屉里会大于等于3块钱。所以A中所说的情况,其实就是所有的情况,也就是B的情况
by xiaoyaozi