Question

If a spherical ball is enlarged so that its surface area is 9 times greater than its original surface area, then the original radius was multiplied by _________.

Answer 1

The surface area of a sphere is $A = 4 \pi r^{2}$ and if the original S.A was is enlarged to have it 9 times greater, the radius would be multiplied by 3 or roughly 2.99626 rounded off to 3.0. 

For example, let us assign values.
Let A=90

A= 90*9 = 810

$90 = 4 \pi r^{2}$    and    $810 = 4 \pi r ^{2}$

the first r is 2.68 and the second r is 8.03

then, $\frac{8.03}{2.68} = 2.99626$  or rounded off to 3.