作者yourself (你，在做什麼呢？)
看板GMAT
標題[問題] PP2-DS-109
時間Fri Aug 22 18:45:02 2008
這題感覺上答案應該是Ｃ，不過詳解上的答案是Ｂ，我看不懂詳解上的思路，有好心
人可以指點一下嗎？
謝謝。
109.
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.
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【答案】B
【思路】
(2) 2x+ 21(x+y) = 130
x+y =6
x=2, y=4……sufficient
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推 cmchen40:(2) 23x+21y=2x+21(x+y)=130 可有一解 08/22 20:27
推 growthme:這種陷阱，真很容易太開心之下，就大力的踩下去了。 08/22 20:33
→ yourself:是因為剛好只有這個解嗎？ 08/22 21:32
→ yourself:而且我有點不太懂改成2x+21(x+y)=130之後要怎麼求x+y，謝 08/22 21:33
推 abib:23x + 21y = 2x + 21(x+y) 是這樣嗎？ XDDD 08/23 00:07