SOLUTION: My friend and i have been working on this math problem and we can't seem to figure it out. We were wondering if someone could help us? Please and Thank You!! We would deeply apprec

Question 305011: My friend and i have been working on this math problem and we can't seem to figure it out. We were wondering if someone could help us? Please and Thank You!! We would deeply apprecaite it!!
Spheres
About two cans of paint are needed to cover the hemispherical dome of the silo. Approximatley how many cans are needed to paint the rest of the silo's exterior? the height is 20m from the bottom to the top of the cylinder and the base is 10m
Found 3 solutions by nerdybill, Alan3354, richwmiller:
Answer by nerdybill(7384)   (Show Source): You can put this solution on YOUR website!
About two cans of paint are needed to cover the hemispherical dome of the silo. Approximatley how many cans are needed to paint the rest of the silo's exterior? the height is 20m from the bottom to the top of the cylinder and the base is 10m
.
Surface area of hemispherical dome:
Area of a sphere = 4(pi)r^2
For the hemispherical dome it is simply half of the area above:
(1/2)4(pi)r^2 = 2(pi)r^2
.
radius (r) is half the base = 10/2 = 5 m
.
area of hemispherical dome = 2(pi)r^2
area of hemispherical dome = 2(3.14)5^2
area of hemispherical dome = (3.14)50
area of hemispherical dome = 157 square meters
.
This means 2 cans of paint per 157 square meters.
.
Area of the rest of the silo:
"circumference" * "height
2(pi)rh
2(3.14)(5)(20)
(3.14)(200)
628 square meters
.
Finally, determine the number of cans needed:
628/157 = 4 cans of paint

Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
About two cans of paint are needed to cover the hemispherical dome of the silo. Approximatley how many cans are needed to paint the rest of the silo's exterior? the height is 20m from the bottom to the top of the cylinder and the base is 10m diameter
--------------------
The surface area of a sphere of radius 5 meters is

Half of that is 50 pi square meters
--------------------------------
The lateral area of the silo is

r = 5, h = 20
Area = 200 pi
That's 4 times the hemisphere, so it's ~8 cans of paint.

Answer by richwmiller(17219)   (Show Source): You can put this solution on YOUR website!
There are problems with the question and the info.
The problem states that the base is 10 meters. Is this circumference or diameter?

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