求教几道最新PREP的数学题目

早上模考的，数学终于上51了。但是在很细心的情况下，居然还错了6道。粗心错3道，还有3道居然想不通答案，请NN们指点指点，谢谢！具体见下：

1. When 1000 children were inoculated with a certain vaccine, some developed inflammation at the site of the inoculation and some developed fever. How many children developed inflammation but not fever?

1.       880 children developed neither fever or inflammation

2.       20 children developed fever

OA: C

题目没有说不存在inflammation和fever都存在的情况啊，为什么C可以？

2. a₁,a₂,a₃….a₁₅

In the sequence shown a_n=a_n-1+K, where 2<=n<=15 and K is nonzero constant. How many of the terms in the sequence are greater than 10?

1.       a₁=24

2.       a₈=10

OA: B

我认为需要两个条件同时满足才能解出a₁和K吧？

3. On the number line shown, is zero halfway between r and s?

1.       s is to the right of zero

2.       The distance between t and r is the same as the distance between t and –s.

给出的图形是一条直线从左到右依次排列r,s,t.

OA: C

我认为通过条件2就可以推出答案了。除非r,s同为0？

When 1000 children were inoculated with a certain vaccine, some developed inflammation at the site of the inoculation and some developed fever. How many children developed inflammation but not fever?

题目就说只接一种VACCINE

When 1000 children were inoculated with a certain vaccine, some developed inflammation at the site of the inoculation and some developed fever. How many children developed inflammation but not fever?

2题，不知这样对不对

2. a₁,a₂,a₃….a₁₅

In the sequence shown a_n=a_n-1+K, where 2<=n<=15 and K is nonzero constant. How many of the terms in the sequence are greater than 10?

1.       a₁=24

2.       a₈=10

已经知道第８项是１０的话，只要知道Ｋ是正是负就可以回答．但是Ｋ没说正负啊，要靠１项啊．我也觉得选Ｃ

3. On the number line shown, is zero halfway between r and s?

1.       s is to the right of zero

2.       The distance between t and r is the same as the distance between t and –s.

给出的图形是一条直线从左到右依次排列r,s,t.

２的情况在Ｓ是负数的情况下不成立

我先弱智地问下，数学错几道，可以还是51啊？

三道题解答如下：

第一题，我感觉题目没有什么错误，因为不管是不是有I和F同时存在的情况，答案都一样.何况问题还问到有I没有F的数，可见他是默认有I,F同时存在的情况的。

第二题，就是选B,确实是个陷阱，我起初做也错了。因为有题目知，这个数列是等差数列，不论K为正或负，a都是递增或递减，而a8为中间的数，两边都有7个数，它是单调的数列，所以，大于a8的数肯定有7个。

第三题，选C吧，只有第二个答案不够，因为有两种可能，r,0,s,t,或者r,s,t,0,只有联合第一个条件，才可以确定是r,0,s,t.

好不明白，请NN解答

FEVER的数量（包括FEVER BUT NOT INFLAMMATION+ 既FEVER又INFLAMMATION）是20

20+ inflammation but not fever的数量=1000-880

谢谢大家！

回Daisy，我用的是PREP Mock，上次错6道是50分，这次就变成51分了。我也搞不懂。不过我估计6-10个差不多50，5个以内51吧。