Question

The radius of a circle is $3$ metres. What is the radius of another circle whose area is $16$ times that of the first?

Answer 1

Ratio of the areas $=1:16$
$\therefore$ Ratio of the radii $=1:4$
This means that if the radius of the first circle is $1m$, it is $4m$ for the second.
$\therefore$ If the radius of the first circle is $3m$, it is $3\times 4$ for the second $=12m$