作者lovetoend (叫我坏人)
看板GMAT
标题Re: [计量] prep 2-ds- 109
时间Fri Jul 4 15:28:27 2008
※ 引述《mauricew (只要健康 就是幸福)》之铭言：
: Marta bought several pencils. If each pencil was either
: a 23-cent pencil or a 21-cent pencil,
: how many 23-cent pencils did Marta buy?
: (1) Marta bought a total of 6 pencils.
: (2) The total value of the pencils Marta bought was 130 cents.
: Answer: B
: 请问如何列式?
23x + 21y = 130 x,y 为0或正整数
求x=?
发现x最多只能到5
只有x=0,1,2,3,4,5 六种可能
所以就是代入法
意外发现哈雷路亚 CHANCE
x=2 y=4 为唯一解
如果代无 大概就是E了
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