【#GRE留學(xué)外語考試# #GRE數(shù)學(xué)重要知識(shí)點(diǎn)：Combinations of Choices#】九層之臺(tái)，起于壘土；千里之行，始于足下。備考的路上，哭過、累過、笑過，但只要堅(jiān)持向前走，終將會(huì)拿到屬于我們的證書。以下是©無憂考網(wǎng)整理的“GRE數(shù)學(xué)重要知識(shí)點(diǎn)：Combinations of Choices”，歡迎閱讀參考！更多相關(guān)訊息請(qǐng)關(guān)注©無憂考網(wǎng)！

　　Combinations of Choices

　　If there are n choices for one type and m choices for second type, then number of combinations for both types is the product of choices:n*m.

　　Example:

　　If there are 3 kinds of breads to choose from and 4 kinds of meats, then we can make 3*4=12 different sandwiches.

　　If an alphabet has 26 letters, then the number of possible 2 letter word is 26*26=676.All of them may not be vaild words.

　　Remember:

　　Do not add the choices to get the total combinations.

　　The product rule can be applied to more than two types of choices: if there are 3 kinds of breads, 4 kinds of meats, and 6 kinds of cheeses, then we can make 3*4*6=72 different sandwiches.