Prep 一題數學

[kotokolin]

Linda, Robert, and Pat packed a certain number of boxes with books. What is the ratio of the number of boxes that Robert packed to the number of boxes of books that Pat packed?

(1) Linda packed 30 percent of the total number of boxes of books
(2) Robert packed 10 more boxes of books than Pat did

答案是E
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我試著看C是不是答案

假設 Linda, Robert, Pat pack的數量分別是L, R, P
可由選項2得 R=10+P 加上選項1
[ p+(P+10) ]/ L= 7 / 3

所以導出 6P+30=7L
我不小心找到 P=2, L=6, 所以R=12

就很高興的選了C .....就錯了....難不成其實這個式子還可以找到其他解@@

[GOBLIN]

here is another possible solutions
P=16, R=26 , L =18

[vantreal]

這個題目用比例法可以看的比較清楚.

(1) + (2)

[ P+ (P+10) ] / total = 7/10
=> (2P +10) / (L + 2P +10) = 7/10
設 A = 2P+10
A/ (L +A) = 7/10
簡化後可得 L = 3/7 A = 3/7 (2P+10)
既然有2個未知數 L 和 P, 就代表有多個解答.

Ans: (E)

[kotokolin]

灰雄感謝呀....

一開始式子列出來了, 覺得應該不只一組解,
但GMAC有時候心機很重, 會有那種式子只有一組答案的....
所以現在都帶數字進去檢查看看是不是真的有很多解~ 真煩惱T_T