Question

Question #cb1f2

Answer 1

`8/20` or `2/5` will be prime

Explanation:

Let's start with what we know:

• We have a spinner with equal sections numbered 1 through 20
• We have 20 sections, so the probability will be out of 20
• Prime numbers are numbers with two factors (one and itself)

NOTE: It is important to realize that, by definition, 1 is not considered a prime number, because it only has one factor, itself.

How many prime numbers are there 1-20?

Prime numbers:
2, 3, 5, 7, 11, 13, 17, 19 (8 numbers). If this seems confusing, ask yourself "do these have any factors other than one and itself?"

We have 8 prime numbers, out of 20 possible. Therefore, our probability of spinning a prime number is `8/20`, which can of course be simplified to `2/5`, if we divide by 4.