pp-T2-DS7

[Huang Hsin-Yi]

7. 462-!-item-!-187;#058&000279
One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee. The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y. Is x < 0.8 ?

(1) y > 0.15

(2) C大於或等於7.30

Ans:B

（1) I do not know C ----insufficient
(2)我用數字　0.9 和　0.7代入　都符合條件----insufficient
(1)(2)x=0.9 y=0.17 x=0.8 y=0.32----------insufficient

so I chose E

[chris8888]

7. 462-!-item-!-187;#058&000279
One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee. The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y. Is x < 0.8 ?

(1) y > 0.15

(2) C大於或等於7.30

Ans:B

（1) I do not know C ----insufficient
(2)我用數字　0.9 和　0.7代入　都符合條件----insufficient
(1)(2)x=0.9 y=0.17 x=0.8 y=0.32----------insufficient

so I chose E

今天小花去考試了, 看來我要再找戰友一起讀書了, 不知道你可以當我的戰友嗎? 一起加油打氣.

以下是解題法, 我也忽略掉這句話.
One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee. The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y. Is x < 0.8 ?

1). Y > 0.15 insufficient
x + y = 1
2). C >= 7.3
x + y = 1
C = 6.5x + 8.5y 聯立方程式, 假設C最小7.3代入計算
x = 1-y
=> 7.3 = 6.5(1-y) + 8.5y
=> 7.3 = 6.5 - 6.5y + 8.5y
=> 7.3 = 2y + 6.5
=> 7.3 - 6.5 = 2y 由此可見, 當C越來越大時, y會變大, x將會變小.

得X=0.6, Y=0.4 sufficient

[Huang Hsin-Yi]

感恩!!終於遇到救星了!!
數學題真是字字珠磯,看漏不得

能當你的戰友真是我的榮幸,不過需要做些什麼
我是每天都在戰拉,要戰的2月20日做最後的掙扎
準備過一個難忘的新年,希望你也會在版上

原來小花去考試,怪不得沒他蹤影,祝福他有個好成績,好心人會有好報的拉