求教2道prep数学题

kittenalways · 发表于 2011-11-6 19:43:08

a certain office supply store stocks 2 size of self-stick notepads, each in 4 colors: b, g,y,p. the store packs the notepads in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size of 3 different colors. if the order in which the colors are packed is not considered, how many different packages of the types described above are possible?
16

of the 60 animals on a certain farm. 2/3 are either pigs or cows. how many cows?
1 the farm has more than twice as many cows as it has pigs
2 the farmhas more than 12 pigs
1+2
why not just 1?

luciecao · 发表于 2011-11-6 19:49:58

well,C(3,4)*C(1,2)+C(1,4)*C(1,2)=8+8=16
2.because the MORE THAN TWICE doesn't equal to TWICE

求教2道prep数学题

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