prep 1-143和139 题请教~

143.

In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best.  If each song was selected 4 times, how many students were surveyed?

(A) 96

(B) 48

(C) 32

(D) 24

(E) 18

答案是D，不会做。

谢谢~

1. first we get the totall number of the songs selected is 12x4=48, and because everyone choose 2, so we have 48/2=24 students.

2. As there'r 15 integers(odd) in the set, and the median is 25, so 25 is the 8th in the queue, and we get a form as follows,

                                        a, b, c, d, e, f, g, 25, h, i, j, k, l, m, n

   and since a,b,c,d,e,f,g are all no more than 25 and h,i...n are above 25,

    so if we want to get the greatest integer in this set, it must be "n",

  whats more, n-a=25, so "a" must be the minimum of all possibilities,

  In this way, a,b,c,d,e,f,g and 25 must be consecutive numbers,

  that is to say, they'r 18,19,20,21,22,23,24,25

  Thus, we get n=25+18=43.

See if they are correct or not.