Your local community wants to raise money to fix one of the playgrounds in your area. Since balloons are popular with young children, your group decides to sell them to make money. You have bought a
box of balloons for $10. You decide to sell the balloons for $1.25 each.
a. How much money will you raise if you sell 25 balloons?
b. How many balloons will you need to sell in order to raise $250.

For every corresponding pair of cross sections, the area of the cross section of a sphere with radius r is equal to the area of the cross section of a cylinder with radius and height 2r minus the volume of two cones, each with a radius and height of r. a cross section of the sphere is and a cross section of the cylinder minus the cones, taken parallel to the base of cylinder, is the volume of the cylinder with radius r and height 2r is and the volume of each cone with radius r and height r is 1/3 pie r^3. so the volume of the cylinder minus the two cones is therefore, the volume of the cylinder is 4/3pie r^3 by cavalieri's principle. (fill in options are: r/2- r- 2r- an annulus- a circle -1/3pier^3- 2/3pier^3- 4/3pier^3- 5/3pier^3- 2pier^3- 4pier^3)