GMATPrep PP Test 1 一題

[meishan]

24.A certain office supply store stocks 2 sizes of self-stick notepads, each in 4 colors:
blue, green, yellow, or pink. The store packs the notepads in packages that contain either
3 notepads in package that contain either 3 notepads of the same size and the same color
or 3 notepads of the same size and of 3 different colors. If the order in whick the colors
are packed is not considered, how many different packages of the types described above are
possible?
A.6
B.8
C.16
D.24
E.32

Ans:C
我怎麼算都是C(2,1)*C(4,3)=8，
請問我是那裡的思考有問題嗎？
謝謝。

[StanleyHuang]

題目說裝法有兩種：
1) 同size同顏色 ==> C(2,1)*C(4,1) = 8
2) 同size不同顏色 ==> C(2,1)*C(4,3) = 8
1) + 2) = 16

[meishan]

感謝感謝~
我一直把數量和種類混在一起了，
一直覺得怎麼可能每種size各四種顏色，
卻還選得出同顏色的(明明是只有四個~)，
看了StanleyHuang的回答，
終於了解。

[chris8888]

yeah, 這題我也搞混了. 現在懂了.

它沒給我們數量, 純粹要我們做出搭配
1. 同size and 同color => C(2, 1) * C(4, 1) <== 有兩個size可選, 每個size有四種顏色
2. 同size and 不同 color => C(2, 1) * C(4, 2) <== 有兩種size可選, 每個size選出三個不同的顏色

合計是16