这条GRE的题，谁懂得做?

Sandy has a husband and 2 children. She brings at
least 1 member of her family to a diner for lunch
every day. The diner offers 10 lunch specials. If no
one orders the same thing, how many different orders
can Sandy’s family make for lunch?
Indicate all possible values.

答案选项分别是45，90，120，210，720, 5040

所有跟帖： 

• 似乎是简单的排列组合问题，但我的算法怎么都对不上啊。可能取决与定义 -abookl- ♀ (386 bytes) () 11/15/2014 postreply 13:37:42

• 你做对了 -bearsback- ♂ (104 bytes) () 11/15/2014 postreply 16:02:25

• Three possible answers: 45/120/210. -ZoyaWashington- ♀ (0 bytes) () 11/17/2014 postreply 21:29:30