If $15 \%$ of the members of a population were affected by a disease and $8 \%$ of those affected died, the mortality rate in relation to the entire population was:
(a) $1.2 \%$;
(b) $1.8 \%$;
(c) $8 \%$;
(d) $12 \%$;
(e) $23 \%$.
The correct option is (a).

The proportion of the entire population that falls ill from the disease is $\frac{15}{100}$, and among those who fall ill, the proportion of those who die is $\frac{8}{100}$. Therefore, the proportion of the population that dies from the disease is $\frac{15}{100} \times \frac{8}{100}$, which corresponds to

$$
\frac{15 \times 8}{100^{2}}=\frac{120}{10000}=\frac{1.2}{100}=1.2 \%
$$