Question

A number is chosen from the numbers 1 to 100. Find the probability of its being divisible by 4 or 6.

Answer 1

Assume p(E1)= probability of event 1 (divisibility by 4)

= $\frac{n\left(E\right)}{n\left(S\right)}=\frac{25}{100}=\frac{1}{4}$

Assume p(E2)= probability of event 1 (divisibility by 6)

= $\frac{n\left(E\right)}{n\left(S\right)}=\frac{16}{100}=\frac{4}{25}$

Also, $n(E1\cap E2)=8$

Thus,$p(E1\cup E1)=p\left(E1\right)+p\left(E2\right)-p(E1\cap E2)$

= $\frac{33}{100}$