Question

What percent of the first 20 natural numbers are prime numbers?

Answer 1

Answer: The required percentage is 40%.

Step-by-step explanation: We are given to find the percentage of the first 20 natural numbers that are prime.

We know that

first 20 natural numbers are 1, 2, 3, 4, . . . , 19, 20.

And, the prime numbers among them are 2, 3, 5, 7, 11, 13, 17 and 19.

So, if S be the sample space for the experiment and A be the event of selecting a prime number.

Then, we have

n(S) = 20 and n(A) = 8.

Therefore, the probability of event A is given by

`P(A)=(n(A))/(n(S))=(8)/(20)=(2)/(5)*100\%=40\%.`

Thus, the required percentage is 40%.

Answer 2

The primes are 2, 3, 5, 7, 11, 13, 17, 19. There are 8 of them, so they make up 40% of the numbers 1–20.