Question

The third proportional to $8,12$ is:

• A. $18$
• B. $8$
• C. $4$
• D. $20$

Answer 1

The correct option is A $18$

The third proportional of two numbers $a$ and $b$ is defined to be that number $c$ such that $a:b=b:c$.

Given that $a=8$ and $b=12$

So, $8:12=12:c$

$\frac{8}{12}=\frac{12}{c}$

$\Rightarrow c=\frac{12\times 12}{8}$

$\Rightarrow c=18$