Test Prep -- DS

[lisayang83]

Of the students who eat in a cafeteria, each student either likes or dislikes lima beans and each either likes or dislikes sprouts. Of these students, 2/3 dislikes lima beans and of those who dislike limba beans, 3/5 also dislikes sprouts. How many students like sprouts but dislikes lima beans?

1. 120 students in the cafeteria
2. 40 like lima beans

Ans : D
i chose b

[dibert8]

dislike B, dislikeS = (2/3)(3/5) = 2/5
dislkie B, like S = 2/3 - 2/5 = 4/15

(1) 120 * 4/15
(2) like B = 1 - 2/3 = 1/3 => total = 40 / (1/3) = 120; 120 * 4/15

[lisayang83]

想請問一下
那喜歡 Sprout 的人 是不是 3/5?
謝謝

[dibert8]

喜歡 S 的人 = 喜歡 B 喜歡 S 的人 + 不喜歡 B 喜歡 S 的人
題目無法推出'喜歡 B 喜歡 S 的人',所以算不出來.

[hey]

其實這種題目用表格會比較好計算:
Lima Dislike Lima Total
Sprout
Dislike Sprout 2/5 (2/3*3/5)
Total 1/3 2/3 1

由條件一或二都可算出答案, 所以選選項(D)

[nemolee]

作題時，題目中間有一小段不太了解，半猜之下，答案寫對了

Of the students who eat in a cafeteria, each student either likes or dislikes lima beans and each either likes or dislikes sprouts. Of these students, 2/3 dislikes lima beans and of those who dislike limba beans, 3/5 also dislikes sprouts. How many students like sprouts but dislikes lima beans?

請問畫底線的地方, 這句藍色的部份... 應該怎麼看? 謝謝
Of these students, 2/3 dislikes lima beans and of those who dislike limba beans, 3/5 also dislikes sprouts

[小花]

在這些學生中2/3不喜歡lima, 而這些不喜歡lima的學生中3/5不喜歡sprouts

[nemolee]

謝謝小花大人