Question

A glass jar contains $20$ red marbles. If a marble is chosen at random from the jar, the probability of not choosing a red marble is .

Answer 1

Total number of marbles in the jar= $20$
Number of red marbles in the jar = $20$

$\text{P(choosing red marble)}=\frac{\text{Number of red marbles in the jar}}{\text{Total number of marbles in the jar}}$

$\Rightarrow \text{P(choosing red marble)}=\frac{20}{20}=1$

We know,
$\text{P(not choosing red marble)= 1 - P(choosing red marble)}$

$\Rightarrow \text{P(not choosing red marble)}=1-1$

$\Rightarrow \text{P(not choosing red marble)}=0$

$\therefore$ The probability that the chosen marble is NOT red is $0$. Hence, the event of NOT choosing a red marble from a jar with all red marbles is an $\text{impossible event}$.