GMAT PP

[lisayang83]

1.) In a xy cordinate plane, line l and k intersect at (4,3), is the product of their slope negative?

a. product of x intercepts of line l and k is positive
b. product of y intercepts of line l and k is negative

Ans. c

不知道這一題要怎麼解

2.) a certain circular area has its center at point p, and has radius 4. Points x+y lie in the same plane as the circular area. Is point Y outside the cricle?

a. distance between P and X is 4.5
b. distance between X and Y is 9

Ans. C
我選E 因為我覺得 point y 有可能是在圈外 , 即使Y在圈外 仍可以符合 X and Y lie in the same plane as the circular area?!

3) Of the 200 members in a club, those that speak German also speaks English, and 70 members speak only Spanish, no members speaks all three. HOw many people speak 2 of the 3 languages?

a. 60 speaks only English
b. 20 does not speak any

Ans. C
我也選 E 以下是我的算法 不知道哪裡錯了

若把兩各條件並起來 會得以下的算式

G+ 60(E) + 70(S) + GE + EF + FG = 180
50 = G + GE + EF + FC
因為 解不出 G 所以不知道 會說兩種語言的人有多少

[elmer0901]

1).這題考點主要是二條線斜率一條是否為正另一條是否為負?
建議用畫圖,你會更清楚!
a.與x軸交點乘積為正,
則可推出二條線斜率乘積為正(若line l and k是同一條線)
或斜率乘積為0(若line l為x=4,line k與x軸交於x>0且過(4,3)
或斜率乘積為負(只要line l和k交於(4,3)且同時x軸交點都>0或<0,方向不同但類似"X"這形狀
所以不充分
b.同理,y軸交點乘積為負=>二條線與y軸交點一必為>0,另一必為<0
故斜率乘積亦有可能=0(若line k為y=3,line l過(4,3)但與y軸交點<0)
或斜率乘積為負
故不充分
二者合併,就可去除掉line l和k是冋一條線或x=4,y=3的組合
所以斜率必為負
希望你看得懂

2).題目不就是問y一定在圓外嗎!

3).題目說講G一定會講E,故G=GE,所以G不須列出
又題目說沒有人會講三種語,故講S一定不會講G,故SG=0(你的S應是打錯成F)
所以50=GE+ES

另外建議樓主一次PO一題,方便以後的人查詢

[chris8888]

3) Of the 200 members in a club, those that speak German also speaks English, and 70 members speak only Spanish, no members speaks all three. HOw many people speak 2 of the 3 languages?

a. 60 speaks only English
b. 20 does not speak any

總人數 = 三種語文都會的 + 只會說兩種的 + 只會說一種的 + 什麼都不會說的
根據題目三種語文都會的 = 0
只會說兩種的 ? <== 題目要我們算的
只會說一種的 => English 60人, German 0人, Spanish 70人
200 = 剛剛好三種都會說的0 + 剛好只會說兩種的x + 只會說一種的60+70 + 正好三個都不會說的20 <== 這是條件(1)+(2)
得出x = 40

答案是C