JAMB 2017 · UTME (set 2) · Q3

Probability
Sets & Venn diagrams

If $U = \{x : x \text{ is an integer and } 1 \le x \le 20\}$ , $E_1 = \{x : x \text{ is a multiple of 3}\}$ and $E_2 = \{x : x \text{ is a multiple of 4}\}$ , and an integer is picked at random from $U$ , find the probability that it is not in $E_2$ .

Worked solution (try it first)

$E_2$ , the multiples of 4 up to 20, is $\{4, 8, 12, 16, 20\}$ , which has 5 members.
So $P(\text{in } E_2) = \frac{5}{20}$
$= \frac14$ .
Not in $E_2$ is the complement: $1 - \frac14 = \frac34$ , option A.

Report a problem with this question