Question

What is the probability of rolling a die and getting a 3 or even number?

Answer 1

A regular die has six sides with numbers 1 up to 6.

Thus, there are 3 even numbers in the die which are 2, 4 and 6.

And there is only one side of the die that has the number 3.

This means that we are looking for 4 possibilities in rolling a die.

Computing the probability, we get:

`\text{ Probability = }\frac{No.\text{ of even numbers + No. of 3s}}{Total\text{ possible numbers}}`
`\text{ = }\frac{3\text{ + 1}}{6}`
`\text{ = }(4)/(6)\text{ = }(2)/(3)`
`\text{ Probability = }(2)/(3)`

Therefore, the probability of getting a 3 or even number is 2/3.

Note:

For "or" scenario, the following equation must be applied:

`\text{ Probability = }\frac{\text{ No. of outcomes for A}}{\text{Total number of outcomes}}\text{ + }\frac{\text{ No. of outcomes for B}}{\text{Total number of outcomes}}\text{ + }\ldots`

For "and" scenario, the following equation must be applied:

`\text{ Probability = }\frac{\text{ No. of outcomes for A}}{\text{Total number of outcomes}}\text{ x }\frac{\text{ No. of outcomes for B}}{\text{Total number of outcomes}}\text{ x }\ldots`