# Probability: A and B

How to find the probability P(A and B): 1 example and its solution.

## Example

Solution

Solution (Detail)

Set A as

picking an odd number from 1 to 10.

{1, 3, 5, 7, 9}

Set B as

picking a prime number from 1 to 10.

{2, 3, 5, 7}

Then [A and B] is,

write the numbers in both A and B,

{3, 5, 7}.

The number of {3, 5, 7} is 3.

n(A and B) = 3

The number of [1 ~ 10] is 10.

n(S) = 10

Then P(A and B) = 3/10.

Probability

So 3/10 is the answer.