Multiple choice

A box contains $20$ cards marked with the numbers $1$ to $20$. One card is drawn from this box at random. What is the probability that number on the card, is a prime number?

  1. $\displaystyle \dfrac{1}{5}$
  2. $\displaystyle \dfrac{2}{5}$
  3. $\displaystyle \dfrac{1}{3}$
  4. $\displaystyle \dfrac{1}{2}$
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B Correct answer
Explanation

Prime numbers between 1 and 20 are 2, 3, 5, 7, 11, 13, 17, 19. There are 8 primes. Probability = 8/20 = 2/5.

AI explanation

The prime numbers between 1 and 20 are 2, 3, 5, 7, 11, 13, 17, and 19, giving a total of 8 favorable outcomes. Using the classical definition of probability, we divide the 8 favorable outcomes by the 20 total possible outcomes. This fraction simplifies to 2 over 5, which is the required probability.

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