Question

Which of the following is proportional to 3:5?

• A. 9:15
• B. 3:17
• C. 1:9
• D. 6:12

Answer 1

The correct option is A 9:15

Two ratios are proportional when they are equal.
Writing all the options in simplest form,

$i)9:159:15=\frac{3\times 3}{3\times 5}=\frac{3}{5}=3:5$

$ii)3:17$
$3:17$ is in its simplest form because there are no common factors between the antecedent and the consequent except 1

$iii)1:9$
$1:9$ is in its simplest form because there are no common factors between the antecedent and the consequent except 1

$iv)6:12$
$6:12=\frac{1\times 6}{2\times 6}=\frac{1}{2}=1:2$

Clearly, only $9:15$ is proportional to $3:5$.