求问PREP题目1道

onemilenorths

If k is a positive integer, is k the square of an integer?
1. k is divisible by 4
2. k is divisible by exactly four different prime numbers

答案B, B是什么思路呢?
谢谢!

onemilenorths

many  thanks @!!!!!

hebbechou

第一题我觉得答案也是E啊.既然是4个不同质数, 那就比方2,3,5,7 最小的数是210. 第二题设selling price is x, then 150+x*40% = x, get x = 250. Profit is 250-150=100.

shuishuiles

Q18:

If k is a positive integer, is k the square of an integer?

(1)   k is divisible by 4.

(2) k is divisible by exactly 4 different prime numbers.

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

                                                                                                  Answer: E

 

这是 GWD 30-18题。一模一样但是答案是 E  头疼阿。。GWD 太多答案都不准了

sinadragon

QUOTE:

以下是引用detectiveyan在2007-1-17 12:31:00的发言：

k is divisible by exactly four different prime numbers

第一个题的第二个条件说恰好被四个不同的质数整除。

也就是说其质因子分解为4个不同质数的成积。

因为每一个数都可以分解为质因子乘积，对于平方数的特点应可以分解为几个质数成绩的平方。如36=（2*3）^2,144=(2^2*3)^2；  所以题目第二个条件不是质数乘积的平方，也就是说一定不为完全平方数。

同意！

detectiveyan

k is divisible by exactly four different prime numbers

第一个题的第二个条件说恰好被四个不同的质数整除。

也就是说其质因子分解为4个不同质数的成积。

因为每一个数都可以分解为质因子乘积，对于平方数的特点应可以分解为几个质数成绩的平方。如36=（2*3）^2,144=(2^2*3)^2；  所以题目第二个条件不是质数乘积的平方，也就是说一定不为完全平方数。

georgeqian

第一题 我也想知道为什么。。。第二题思路是 假设那个所谓的 markup is X THEN   40%(150+X)=X  得出结果为100。。你也可以返回去把数字带进去检查。。。。不知道对你有没有帮助。

onemilenorths

a furniture dealer pruchased a desk for $150 and then set the selling price equal to the pruchase price plus a markup that was 40 percent of the selling price. if the dealer sold the desk at the selling price, what was the amount of the dealer's gross profit from the purchase and the sale of the desk?
$40; $60; $80; $90; $100
the answer is 100;

再来一道！