问个prep模靠的数学题

MUYU · 发表于 2012-4-15 05:22:13

A certain basket contains 10 apples, 7 of which are red and 3 of which are green.If 3 different apples are to be selected at random from the basket, what is the probability that 2 of the apples selected will be red and 1 will be green?

答案是21/40

我怎么算的是7/40？不应该是C7 2*C3 1/C10 3吗？

泾渭不凡 · 发表于 2012-4-15 05:49:27

姐姐的计算公式是对的哈。
是不是运算出现问题了哈？
C72*C31/C10 3=((7*6/2)*3)/(10*9*8/3*2)=21/40

问个prep模靠的数学题

所属分类: GMAT考试

正在浏览此版块的会员 ()

浏览过的版块