我用1000圓買了三種零食共100包, chocolate 50元, potato chip 10圓, candy 2包1元問:我買了多少 chocolate, potato chip 和 candy?本人恨中打要過程(此題孫老師不要做)沒過程就別答,腦力激動吧!
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設chocolate買X包 potato chip 買Y包 candy買(100-X-Y)包則可列出50X+10Y+1/2(100-X-Y)=1000100X+20Y+100-X-Y=200099X+19Y=190099X=1900-19Y99X=19(100-Y)則X為19的倍數所以X=19 Y=1則chocolate買19包 potato chip 買1包 candy買80包
potato chip買100包,價錢符合把一包potato chip換成一包candy: 省9.5元把一包potato chip換成一包chocolate: 虧40元使虧損剛好抵銷;40*chocolate = 9.5*candy80*chocolate = 19*candycandy = 80, chocolate = 19