请教一道排列组合的数学题

cindyzhoulanbj

这道题咋整呢？

How many different ways can 3 cubes be painted if each cube is painted one color and only the 3 colors red, blue, and green are available? (Order is not considered, for example, green, green, blue is considered the same as green, blue, green.)

miyazheng

3cube一个颜色：3种
两个颜色：3*2=6种
三种颜色：1种
总共10种

Ttian95

C13=3; C23=6;C33=3 -> 3+6+3-2=10