8\% of the people eligible to vote are between 18 and 21 years of age. In an election, 85\% of those eligible to vote, who were between 18 and 21, actually voted. In that election, the number of persons between 18 and 21, who actually voted, was what percent of those eligible to vote?
(a)4.2
(b)6.4
(c)6.8
(d)8
Answer
Answer (as printed): C
Explanation
Let the number of persons eligible to vote be $x$. Then, Number of eligible persons between 18 and 21 = 8\% of $x$. Number of persons between 18 and 21, who voted = 85\% of $(8 \%$ of $x)=\left(\frac{85}{100} \times \frac{8}{100} \times x\right)=\frac{68}{1000} x$. $$\text { ∴ } \text { Required percentage }=\left(\frac{68 x}{1000} \times \frac{1}{x} \times 100\right) \%=6.8 \% .$$
Explanation as extracted from the printed page; notation may be imperfect.