Question

On a spinner, `P(3) = 2/5` and the `P(4) = 3/8`, what is the probability of getting 3 or 4?

Answer 1

`2/5+3/8=16/40+15/40=31/40`

Explanation:

Let's think about a regular, fair die for a second. There are 6 sides and so the probability of rolling a 1 is `1/6`. The probability of rolling a 2 is also `1/6`. The probability of rolling a 1 or a 2, therefore, is the probabilities of each one occurring added to the other:

`1/6+1/6=2/6=1/3`

And so with the spinner, we do the same thing - we add the probabilities together:

`2/5+3/8=16/40+15/40=31/40`