There are 8 disks in a container that are numbered 23, 24, 25, 26, 28, 29, 30 and 31. 4 disks are randomly removed from the container, one after the other, without replacement. Then a list of 5 numbers containing the 4 numbers on the disks selected, together with the number 27 will be made. What is the probability that 27 is the median of the list of 5 numbers?
Choose the most appropriate option.
A) 2/5	B) 17/35	C) 1/2	D) 18/35	E) 5/9
we must consider that there are two ways to choose from A or B, and then two ways to choose each number from their respective groups:   Group A (23,24,25,26) and Group B (28,39,30,31). Then we saw that in order to have a median of 27 we need to have 2 from group and and 2 from group B.   The probability of that is 4/8 x 3/7 x 4/6 x 3/5 x (1/2) x (1/2) = 18/35.   Answer: 18/35.
<result>D</result>
There are 8 disks in a container that are numbered 23, 24, 25, 26, 28, 29, 30 and 31. 4 disks are randomly removed from the container, one after the other, without replacement. Then a list of 5 numbers containing the 4 numbers on the disks selected, together with the number 27 will be made. What is the probability that 27 is the median of the list of 5 numbers?