Question 1018951
So we need to know a couple of things in order to solve this problem. The formulas for the area of a rectangle and of a circle. 

A rectangle is the width * height. A circle is the {{{pi * radius ^ 2}}}.

So, if we know how much area we want for the circle we can solve the following equation for the radius

{{{Area = pi * radius^2}}}

The garden is currently 30 * 36 = 1080 sq feet. We want it to be 40% bigger so we can multiple 1080 by 1.4 = 1512 sq feet.

1512 is the area we want so now we find the radius by dividing by pi and taking the square root. Keep in mind that the problem is asking for "how wide" is the circle which means they want the diameter, not the radius so you will have to multiply the radius you found by 2.