prep 数学 DS题（易错）救助 3月考的同学进来看看吧

banbanshu

今天做了一堆DS题。下面几道是我认为有问题的。同学们发表点意见啊。


45.    3906-!-item-!-187;#058&003579      C
How many of the 42 people in a group are employed students?

(1)  29 of the 42 people are employed.

(2)  24 of the 42 people are students.

答案是E  难道是因为题中没有说只有这两种人？


64.    5320-!-item-!-187;#058&004563       E              
Are at least 10 percent of the people in Country X who are 65 years old or older employed?

(1) In Country X, 11.3 percent of the population is 65 years old or older.

(2) In Country X, of the population 65 years old or older, 20 percent of the men and 10 percent of the women are employed.
这道题大家仔细看看吧。个人觉得答案错了。和机经里的一道争议题异曲同工啊。答案给的是B


    6946-!-item-!-187;#058&005390      E
If the terms of a sequence are t1, t2, t3, . . . , tn, what is the value of n ?

(1)  The sum of the n terms is 3,124.

(2)  The average (arithmetic mean) of the n terms is 4.


这道题也是题意问题。都没给出数列通项。而且求得是n 而不是tn啊



119.    12086-!-item-!-187;#058&008079    C  
A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight.  What is the value of x ?

(1) y = 10

(2) z = 16
答案给的是D    难道液体混合体积可以直接相加吗？太诡异了

banbanshu

大家重点看看 64吧~~~

banbanshu

突然醒悟了 64 B就ok了。还是很容易错啊

roddysong

溶液不可以，溶质可以。比如1单位苹果加3单位水兑4单位的果汁，那么4单位的果汁加上8单位的果汁里面就有（1+2）单位的苹果，应该是这样

yarndyed

题目中一直在说重量，和体积没有关系，重量当然可以相加

心诚则灵的MM

大家重点看看 64吧~~~

-- by 会员 banbanshu (2011/3/4 22:31:55)

64题我是这么想的。
看B，如果男性为X，女性为Y,那么此65岁及以上受雇者为：0.2x+0.1Y
即比较0.2x+0.1Y是否大于0.1（X+Y)
通分后：2x+y与x+y比较，显然B肯定能满足提干的10%为受雇者。

不知上述思路正确？

rainbow582

心诚则灵MM又漂亮，又热心，数学又好。完美！

pmoaprikn

问一下64
(2) In Country X, of the population 65 years old or older, 20 percent of the men and 10 percent of the women are employed.
我理解是:  大于等于65岁的人之中,有20%M与10%W在工作
既然这样这个范围的比例怎么可以跟全部人口比呢??
是我哪里理解错了吗??请NN帮我一下~

molynca0717

If the terms of a sequence are t1, t2, t3, . . . , tn, what is the value of n ?

(1)  The sum of the n terms is 3,124.

(2)  The average (arithmetic mean) of the n terms is 4.

请问这道正确答案是C么

lyria

这题读题要仔细，题干意思是“X村65岁以上人口中是不是至少10%在就业？”而不是“该村是不是至少10%的人口既大于65岁又就业”
所以，不需要跟全部人口比。

问一下64
(2) In Country X, of the population 65 years old or older, 20 percent of the men and 10 percent of the women are employed.
我理解是:  大于等于65岁的人之中,有20%M与10%W在工作
既然这样这个范围的比例怎么可以跟全部人口比呢??
是我哪里理解错了吗??请NN帮我一下~

-- by 会员 pmoaprikn (2011/3/7 18:15:26)