Question

A box contains 20 cards, numbered from 1 to 20. A card is drawn from the box at random. Find the probability that the number on the drawn card is prime.

Answer 1

Given: A box contains cards numbered 1 to 20; one card is drawn at random.

Step-wise calculation:

1. Total possible outcomes = 20.

2. Favorable outcomes = Cards showing a prime number.

Primes between 1 and 20 are 2, 3, 5, 7, 11, 13, 17, 19.

So, number of favorable outcomes = 8.

3. Probability = `"Number of favorable outcomes"/"Total outcomes"`

= `8/20`

= `2/5`

= 0.4

The probability that the drawn card shows a prime number is `2/5` or 0.4.