[問題]GWD30-31

[racherlin]

Q31:
There are 5 cars to be displayed in 5 parking spaces with all the cars facing the same direction. Of the 5 cars, 3 are red, 1 is blue, and 1 is yellow. If the cars are identical except for color, how many different display arrangements of the 5 cars are possible?

A. 20
B. 25
C. 40
D. 60
E. 125

答案是 A

這類的問題我一直不會 得慢慢排出來才知道答案
可以請教算式嗎?
謝謝

[kwtluck]

5輛車進行排列組合,有三輛顏色相同
則算式為(5階)/(3階)=(5*4*3*2*1)/(3*2*1)=20

[racherlin]

想請問 如果有六台車
三紅二藍一黃
這樣該怎麼算?
是不是(6階)/(3階)x(2階)=60
謝謝

[kwtluck]

沒錯
(6階)/(3階)*(2階)=60