求助几道PREP上数学

weideng

22.       1599-!-item-!-187;#058&000810

Of the 800 sweaters at a certain store, 150 are red. How many of the red sweaters at the store are made of pure wool?

 

(1)  320 of the sweaters at the store are neither red nor made of pure wool.

 

(2)  100 of the red sweaters at the store are not made of pure wool.

这题答案B,我选E,因为2中not made of pure wool不能说明剩下的就是made of pure wool,可能是别的做的呢?

 

23.       1653-!-item-!-187;#058&000843

At least 100 students at a certain high school study Japanese. If 4 percent of the students at the school who study French also study Japanese, do more students at the school study French than Japanese?

 

(1)  16 students at the school study both French and Japanese.

 

(2)  10 percent of the students at the school who study Japanese also study French.

这题答案B,我选C,我觉得光2推算不出,求思路.

谢谢

丫丫兔

T23:

~F:只学法语的人 J:只学日语的人

(1)已知=> 4%*F=16  =>F， 但J是at least 100,所以不能确定J,F的相对比例。

(2)已知=> 10%*J=4%*F  => J,F的比例，不一定要具体算出，便知JF哪个多哪个少了。

以上~

weideng

谢谢LSMM,那谁可以跟我说说第一题捏~~

bemyselfch

不是纯毛做的，不就是其他材料作的吗？

“红色羊毛衫中有100件不是纯毛做的（也就是用处纯毛以外其他材料作的）”，那剩下的不就是纯毛做的了吗？！

 

weideng

说的在理,早上做的时候突然想不通,呵呵