How do you figure out how much water it takes to fill a swimming pool that is 18 feet round and 4 feet deep?

Answer 1

It's a perfect circle? Is it 18ft across or 18ft around the edge? If it is 18ft across then the radius is 9 feet and the volume (amount of water needed) is going to be (pi)x (r squared)= 81pi which is about 254.469 square feet x 4 feet in height = 1018 cubic feet. A cubic foot is about 7.5 gallons so you need 7634 gallons of water to fill your pool. If it is 18ft around the edge then 18ft=2(pi)(r) 9=(pi)(r) r= 2.86ft (which would mean that your pool is about 5.75 ft across) then we use the same volume formula from above Volume = Area of the circle(that forms the bottom) x Height. Area of the Circle is pi(r squared) where r is half of the distance across the pool. Called the radius. r in this case is 2.86 so (2.86 squared) x pi = 25.78. Multiply by the height (4ft) gets you 103.13 cubic feet. 1 cubic foot is about 7.5 gallons so multiply by 7.5 and you get 773.5 gallons to fill your pool. You figure it out by getting the volume of the cylinder (pool's shape) which is the area of the cirle on the bottom x the height and then multiplying that answer by the conversion factor for cubic feet to gallons. Hope this helps!