50th Percentile is Median NOT mean

I was confused whether 50th Percentile is Mean or Median. So, I will noted down right here that it is MEDIAN

Imagine that there are 9 people in a room. Some are children, teenagers, and adults

These are their age sort in ascending.

5, 10, 15, 20, 25, 30, 35, 40, 45

From the dataset above:
Median = 25
Mean = 25

Calculate median:
Median position = (n+1)/2 
with n = 9 the median position is 5, which is 25

Calculate mean:
(5+10+15+20+25+30+35+40+45)/9 = 25

In this case, the mean and median is equal due to the age is symmetrically distributed

On the other hand, if the people in the room is mostly young, those young kids will make the group look younger.

Although the middle person is 20, the majority is so young that the mean goes down.

1,2,3,4,5,20,21,22,30

Median = 20
Mean = 12

And when majority of the group is older, the mean will rise and become higher

18,19,23,30,43,60,65,70,90

Median = 43
Mean = 46.44