2007-06-23 16:21:44 · 7 answers · asked by Brenda 1 in Science & Mathematics ➔ Mathematics
The surface area of a sphere is 4pir^2.
Knowing the diameter we can find the radius.
The radius is 5.
4pi(5)^2=SA
4pi25=SA
100pi=SA
So the surface area of the sphere is 100pi.
Pi~3.14
The surface area is around 314
314/100=xgallons
3.14gallons to paint the sphere.
PiGallons is the exact answer.
2007-06-23 16:26:53 · answer #1 · answered by Anonymous · 1⤊ 0⤋
The surface area of a sphere is A = 4*pi*r^2,
The radius of a sphere is 1/2 its diameter. IN this case r = 10/2 = 5 ft.
So its surface area is 4* pi * 5^2 = 4 * pi * 25 = 100 * pi = 314.159265358979... sq. ft.
So if one gallon covers 100 sq ft, you'd need 3.14... gallons.
If you have to buy the paint in units of 1 gallon, then you'd need 4 gallons.
2007-06-23 16:29:30 · answer #2 · answered by Tony The Dad 3 · 1⤊ 0⤋
Ok this is how to do it:
Use sphere area formula: 4(pi)r^2 = A. So r = 5 here and thats A = 100pi which is about 314 sq ft. So it would be 3.14159 gallons of paint needed for this job.
You can do this w/o a calculator, it simple moving around decimals.
2007-06-23 16:27:00 · answer #3 · answered by splintercellgod17 2 · 0⤊ 0⤋
Area of a sphere = 4 pi r^2
4*3.14*25 = 314 square feet
314 square feet * 1 gal/100 square feet = 3.14 gal
You need 3.14 gallons, but if you're buying in gallon cans, then you'll have to buy 4 gallons.
2007-06-23 16:27:56 · answer #4 · answered by ecolink 7 · 1⤊ 0⤋
sq feet 1 gallon paint cover
2016-05-18 23:05:18 · answer #5 · answered by ? 3 · 0⤊ 0⤋
Try "surface area of a sphere" in a search engine
2007-06-23 16:25:21 · answer #6 · answered by a²+b²=c² 4 · 0⤊ 1⤋
pi gallons, or 3.14 gallons
2007-06-23 16:26:24 · answer #7 · answered by Alex 1 · 0⤊ 1⤋