超難的概率題

Key word is double-flavor (兩種口味的) ice cream .

No children buy the same combination of flavors and all possible combinations of flavors are chosen.


C(10,2)

=45

There are 45 children.





圖片參考：http://ts3.mm.bing.net/th?id=H.4581507196126670&pid=15.1


2013-09-02 18:57:52 補充：
係啵!上次未答你^^"
果2題係中五學架.

超難的概率題

1. An ice cream shop sells ice cream at 10 different flavors.A group of children come to the shop and each buys a double-flavor ice cream.No children buy the same combination of flavors and all possible combinations of flavors are chosen.How many children are there?

1.一家霜淇淋店賣 10 種不同口味的霜淇淋。一群孩子來到店裡，每個買雙味霜淇淋。沒有孩子買相同的組合的口味和風味的所有可能組合的選擇。有多少個孩子？

解題:
方法步驟1: 把10種口味雪糕代入以下口味:
1.朱古力 2.綠茶 3.芒果 4.云尼拿 5.草莓 6.咖啡 7.牛奶 8.香橙 9.曲奇 10.薄荷

步驟2: 列出可能:
(1)1&2 ;1&3 ;1&4 ;1&5......1&10 [共10個孩子]
(2)2&3 ;2&4 ;2&5 ;2&6......2&10 [共9個孩子]
(3)3&4 ;3&5 ;3&6; 3&7......3&10 [共8個孩子]

****如此類推****
把每次孩子數目減1至no.10口味,便得知答案:
答案:
10+9+8+7+6+5+4+3+2+1= 55 [即55個孩子]