Question

What is the probability of not getting a prime number when a die is rolled?

• A. $\frac{1}{3}$
• B. $\frac{1}{2}$
• C. $\frac{3}{5}$
• D. $\frac{2}{5}$

Answer 1

The correct option is B $\frac{1}{2}$

A die has 6 numbers out of which 3 numbers (2,3 and 5) are prime.
Therefore,
The probability of getting a prime number = $\frac{3}{6}$ = $\frac{1}{2}$

We need the probability of not getting a prime number.
i.e, we need the probability of the complementary event.
Hence, the probability of not getting a prime number = $1-\frac{1}{2}=\frac{1}{2}$