绿皮上的几道题

1.Which of the following procedures is always equivalent to adding 5 given nembers and then dividing the sum by 5?

(1)Multiplying the 5 numbers and then finding the 5th root of the product.

(2)Adding the 5 numbers, doubling the sum, and then moving the decimal point one place to the left.

(3).Odering the 5 numbers numerically and then selecting the middle number.

答案：（2）正确  

我的答案是相反的，所以恳请NN们解释一下提干，谢谢！

2.If positive integer x is a multiple of 6 and positive integer y is a multiple of 14, is xy a multiple of 105?

(1) x is a multiple of 9

(2)y is a multiple of 25.

答案:B     请指教

3.Seven different numbers are selected from the integers 1 to 100. and each number is divided by 7. What

  is the sum of the remainders?

(1) the range of the seven remainders is 6

(2)The seven numbers selected are consecutive integers.

答案：B 

A是怎么排除的？ 我试了好多情况，好像（1）和（2）是一回事？

4.If x,y,p,and q are positive, is x>=y?

 (1) px/qy=p/q

 (2) xy=p

答案：A   我的疑问是：（1）得出x=y,可是这并不能判断出x>=y呀？

题目有点多，希望大家捧场