MAth
posted by Jessica on .
A sphere has a surface area of 28.26 in2. Find the diameter in inches, of the sphere. Use PI
Question 2
What is the surface area, in square inches, of a sphere with radius 3.5 in.? Use Pi and round your answer to the nearest hundredth, if necessary.
Question 3
Whats is the volume of a sphere with a radius of 18 cm?
LAST QUESTION
What is the volume of a sphere with a diameter of 23 in.?
Round to the nearest tenth.
A 1807.5
B.1982.4
C.2103.6
D.2027.8

1. a = 4pi*r^2
28.26 = 4*3.14*r^2
r = 3/2, so diameter = 3
2. use above formula
3. v = 4/3 pi r^3 = 4/3 * 3.14 * 18^3 = 24416.64
4. use above formula. To estimate, 4/3 * pi is about 4. 4*11.5^3 = 6083. Hmmm. Nothing close. (?) 
A = 4 pi r ^ 2
A = 28.26
28.26 = 4 pi r ^ 2
28.26 / ( 4 pi ) = r ^ 2
r ^ 2 = 28.26 / ( 4 * 3.14 )
r ^ 2 = 28.26 / 12.56 = 2.25
r = sqrt ( 2.25 ) = 1.5 in
Question 2
A = 4 pi r ^ 2
A = 4 * pi * 3.5 ^ 2
A = 4 * 3.14 * 12.25
A = 153.86 in ^ 2
Question 3
V = 4 * pi * r ^ 3 / 3
V = 4 * 3.14 * 18 ^ 3 / 3
V = 4 * 3.14 * 5832 / 3
V = 73249.92 / 3
V = 24416.64 in ^ 3
LAST QUESTION
V = 4 * pi * r ^ 3 / 3
V = 4 * 3.14 * 23 ^ 3 / 3
V = 4 * 3.14 * 12167 / 3
V = 152817.52 / 3
V = 50939.1733 in ^ 3
V = 50939.2 in ^ 3
rounded to the nearest tenth 
What is the radius of a sphere that has a surface area of 12.56 ? Use 3.14 for .
Recall the formula .