Question

How many gallons of paint are needed to paint one coat, if a gallon of paint covers 400ft squared?

Answer 1

Answer:

6.28 gallons

Step-by-step explanation:

first we need to find the area of a half sphere, and then find how much paint will be needed for that area.

The area of a sphere:

$a=4 \pi r^2$

thus, the area of half a sphere is:

$a=2 \pi r^2$

we know that the radius is:

$r=20ft$

we substitute this to find the area of the half sphere (the area they need to paint):

$a=2\pi (20ft)^2\\a=2(3.1416) (400ft^2)\\a=2,513.27ft^2$

now the question is how many gallons of paint are needed to paint 2,513.27 square feet.

We are told that 1 gallon covers 400 square feet

thus, we must divide 2,513.27 by 400:

$\frac{2,513.27ft^2}{400ft^2} =6.28$

6.28 gallons of paint are needed.