# Basic Probability

##### New Member
I need some help getting started with this question.....

There N quantity of tourists on a bus and there are n quantity of children amongst them.

When the bus stopped m tourists got off. Please find the probability of that thing, that amongst m tourists that got off there are k children.

Tourists N=12
Children n=8

Number of tourists m who got off the bus = 4
Number of children k who got off bus = 3

#### Statstastic

##### New Member
Hi,
You have 8 children and 4 adults on a bus. 4 people get off the bus.
What is the probability that 3 of the 4 are children?

Ignoring the order for a moment,
think about the first person to get off the bus. What is the probability that it is a child? What's the probability that a second child gets off? Calculate the probability that 3 children and then 1 adult get off the bus.

Now, the order they get off the bus doesn't matter, so you have to multiply by the number of ways of picking 3 out of 4. This is the same as the number of combinations of 1 out of 4.

Hope this helps!