How do I figure out how many gallons of water are in a 4-feet deep, 18-feet around swimming pool?

Sort of a follow-up to another question.How do I figure out how many gallons of water are in a 4-feet deep, 18-feet around swimming pool?
18 = 2 pi r. you need to find pi r squared and then multiply that by 4. then from there, you will find the total number of cubic feet of water and then multiply that by the number of gallons in each cubic foot. so you find that r = 18 / (2 pi), or 9/pi. so pi (81/(pi squared) is pi r squared. so then you have 81/pi as the area of the circle. 81 divided by pi is roughly 25.8, multiply that by 7.48 gallons per cubic foot and by 4 for the height, and you get 772 gallons, so if i were you, i'd just use the hose and leave the milk jugs out of the filling of the pool process.How do I figure out how many gallons of water are in a 4-feet deep, 18-feet around swimming pool?
Find the volume of the cylinder of water.


18 feet = the circumference = 2*pi*r


2*pi*r=18


pi*r=9


r=9/pi





Cylinder volume = area of base times height.


Area of base = pi* r^2


= pi * (9/pi)^2


= 81/pi square feet





Volume = 81/pi * 4 = approximately 103.15 cubic feet





Convert cubic feet to gallons.


771.6 gallons (approximately)





Use website for conversion.


http://www.hoptechno.com/nightcrew/sante鈥?/a>
Find out how many gallons of water are contained by one cubic foot then find the number of cubic feet there are in the pool, multiply this number by the first one.
first find the volume of your swimming pool and the formula for that is are of base multiplied by its height.





Now the dilema is i do not know wether 18 ft. is a circumference or the diameter of the base but lets say it is the diamete and the formula for the area of a circle which is the base of your swimming pool is





Area of a circle = 1/2 pi r^2





now the formula for r is d/2 and the pi is constant value of 3.14





and when you find your swinmming pools' volume then you can compute for the volume of water that you need
since the pool is rounded its volume


will be V= Area of the base times deep.


Area of the base= 18 ft虏 ; deep=4 ft





V= 18*4=72 cu ft.


since 1cu ft= 7.48 gallons


V= 72(7.48 gallons)=538.7 gallons.
The volume v of the pool is given by:


v = pi r^2 h .....(1)


where h is the depth and r is the radius.


If c is the circumference, then:


c = 2pi r, and r = c / (2 pi) ..........(2)


Substituting for c from (2) in (1) gives:


v = hc^2 / 4 pi.


Putting c = 18ft, h = 4ft., and pi = 3.142 gives:


v = 4 * 18^2 / 4 pi = 103.119ft^3


This is equivalent to 103.119* 1728 in^3.





In a UK gallon, there are 277.42 in^3, which would give the capacity of the pool as 103.119 * 1728 / 277.42


= 642.3 gal.





There are different conversion factors for other gallons, such as the US gal. For these, see:


http://en.wikipedia.org/wiki/Gallon

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