This solution to this problem is predicated on the fact that the circumference is just:
. A straight line going through the center of the garden would actually be the diameter, which is well known to be two times the radius of the circle, so we can say that the circumference is just:

So, solving for both the radius and the diameter gives us:

So, the length of thes traight path that goes through the center of the guardain is just
, and we can use the radius for the next part of the problem.
The area of a circle is
, which means we can just plug in the radius and find our area:

So, we have found our area(
) and the problem is done.
1/3= 5/15
2/5= 6/15
5/15 + 6/15 = 11/15
15/15 - 11/15 = 4/15
Part C= 4/15
If you multiply 5.06 by 47.058 you will get 238.11348
What you don't want is the value of r(t) becoming negative. Surely that would represent water escaping the reservoir.
How big can (t) get before water actually starts escaping the reservoir?
Essentially, to figure this out r(t) would have to be equal to 0.
700 - 40t = 0
40t=700
t=700/40=17.5
So the first answer is 17.5 seconds. After this amount of time has elapsed the reservoir will start to lose water as r(t) would become negative.
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The reservoir had the least amount of water in it before it was being filled. That was when t=0. The volume of water in the reservoir wasn't negatively impacted as not enough water had escaped it during the 17.5 to 30 second period.