What is the probability of getting a prime number from the first 20 natural numbers?

Concept: Probability of getting probability of the occurrence of an event is$P\left(E\right)=\frac{\text{Total number of favorable outcomes}}{\text{Total number of outcomes}}$.

We have given 20 natural numbers.

That is, $n\left(S\right)=20$

There are 9 prime numbers in the first 20 natural numbers that are 2, 3, 5, 7, 9, 11, 13, 17, 19.

$E$ is the event of getting a prime number from first 20 natural numbers.

Now, $n\left(E\right)=9$

Thus, $P\left(E\right)=\frac{n\left(E\right)}{n\left(S\right)}=\frac{9}{20}$

Hence, the probability of getting a prime number from the first 20 natural numbers is $\frac{9}{20}$.