Geometry
posted by Mary on .
A wooden cylinder with a diameter of 10 centimeters and a height of 20 centimeters rests on its circular base. It is cut in half horizontally. What is the difference between the combined surface areas of the two newly created cylinders and the total surface area of the original cylinder?
These are my choices:
a. 100rr sq cm
b. 50rr sq cm
c. 25rr sq cm
d. 0 sq cm
I came up with 100rr sq cm??

JESUS

big cylinder = 2π(5^2) + 2π(5)(20) = 300π
smaller = 2π(5^2) + 2π(5)(10) = 200π
but we have two of those, so the new surface area is 400π
difference is 100π
you are correct is the "rr" is supposed to be π 
A cylinder has a height of 16 cm and a radius of 5 cm. A cone has a height of 12 cm and a radius of 4 cm. If the cone is placed inside the cylinder as shown, what is the volume of the air space surrounding the cone inside the cylinder? (Use 3.14 as an approximation of .)