求助PREP 上的数学题

yanqing

If p is a positive odd integer, what is the remainder when p is divided by 4 ?

 

(1) When p is divided by 8, the remainder is 5.

 

(2) p is the sum of the squares of two positive integers.？？？？？？？？？

飞不高

以下是引用yanqing在2009-6-1 17:19:00的发言：

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.B   但是题目中没有对条件进行假设啊？？？？存在还有其他质料的SWEATER啊？？？

total 800, red 150,

(1) neither red nor pure wool 320, so 320 are out of (800-150), can not justify the pure wool red, not sufficient

(2) of 150, 100 not pure wool, so pure wool red sweater is 50, sufficient

B

飞不高

以下是引用yanqing在2009-6-1 17:19:00的发言：

If p is a positive odd integer, what is the remainder when p is divided by 4 ?

 

 

(1) When p is divided by 8, the remainder is 5.

 

 

(2) p is the sum of the squares of two positive integers.？？？？？？？？？

(1), p=8a+5=8a+4+1, the remainder is 1;

(2), since p is a positive odd, so p=m^2+n^, m, n, must be one odd, the other even, if m=2a, n=2b+1

p=(2a)^+(2b+1)^=4a^2+4b^2+4b+1, the remainder is 1,

so d

lulu_judy

是不是选B呢？red sweaters 可以分为made of pure wool 和not made of pure wool

根据2应该可以得出有50件made of pure wool

yanqing

多谢指点啊！！谢谢了