[問題]GWD21-Q20

[hccill]

因為我搜尋搜不到,所以就來發問囉~

Q20
Of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?

(1)The farm has more than twice as many cows as it has pigs.
(2)The farm has more than 12 pigs.

答案是C

可是我覺得答案應該是A吧~
我的想法是:
cows=c, pigs=p

c+p=60*2/3=40
再加上條件(1)=>c>2p
則若c=2p時,可求出p=40/3=13又1/3(不合)
但當p=14時,c=26<2p=28(和條件一相違背)
故p=13,c=27
=>充分

另外,條件二單獨並無法求出c為多少=>不充分

還請大大告訴我,我錯在哪呢??

為何答案是C阿??

謝謝喔~

[angelat]

題目給的條件：C+P=40
第一個條件：C>2p

在這兩個條件之下可以找到的解有：
(C,P)= (30, 10), (29. 11). (28, 12), (27, 13)
可能有四種答案，所以只有(1)不充分

如果加上第二個條件
答案就只剩下 (27, 13)這一組
就可以知道 C=27

[hccill]

喔喔喔....

感恩感恩....

原來如此阿~

是我疏忽了~

謝謝喔!