Forty percent of the first 20 whole numbers are prime. How many of the first 20 whole numbers are prime?

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.

Step-by-step explanation:

We are given to find the percentage of the first 20 natural numbers that are prime.

We know that  the 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 x 100% = 40%

Thus, the required percentage is 40%.  

the circle one

yes yes yes yes yes yes yes yes yes