# Percentage and probability

#### informedman

##### New Member
I have this problem I am trying to solve and I am not sure how. Lets say 70% of the demography is white people. Now if I randomly pick 100 people from the same demography, how do I calculate what is the probability there are exactly 70 white people? or more general question, how do I calculate the chances that there are exactly X white people?

Excuse me if this is a noob question.

#### Dason

##### Ambassador to the humans
You should investigate the binomial distribution. Although if you have a small population you should also look into the hypergeometric distribution.

#### informedman

##### New Member
Thats a great tip. If I use Bernoulli's probability mass function f(k;n,p), in the specific example above p = 0.7, k = 70, n=100?

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#### Dason

##### Ambassador to the humans
Thats a great tip. If I use Bernoulli's probability mass function f(k;n,p), in the specific example above p = 0.7, k = 70, n=100?
Sounds about right to me.