Question 269738
A circular garden is surrounded by a sidewalk with a uniform width of 14 feet. The total area of the sidewalk equals the total area of the garden. How many feet are in the diameter of the garden? Round your answer to the nearest whole number.
:
Let r = radius of the garden
then
(r+14) = radius of the garden and walkway
:
From the given information we know the overall area = twice the garde area
:
{{{pi*(r+14)^2}}} = 2({{{pi*r^2}}})
divide both sides by pi
{{{(r+14)^2}}} = ({{{2r^2}}})
FOIL
{{{(r^2+28r+196)}}} = ({{{2r^2}}})
{{{(r^2-2r^2+28r+196)}}} = 0
{{{(-r^2+28r+196)}}} = 0
{{{(r^2-28r-196)}}} = 0; multiplied by -1
Use the quadratic formula to find r: a=1; b=-28; c=-196
Positive solution: r = 33.8
then
33.8 * 2 = 67.6 ~ 68 ft is the diameter of the garden