how to solve these geometry problems? please help?

Question

- the goalie for the girls water polo team loves pie. after they win the state championship game she and her team are celebrating with all sorts of sweets including the goalies favorite: PIE. However, she doesn't like the crust; she always gives that to her teammate. If the goalie give away 13.1 inches of crust which creates a central angle of 60 degrees what is the diameter of the PIE that has been ordered to the nearest tenth inch? 
(He gives us the answer which is 25.0 but he hasnt showed us to work it! Help!)

-The dome of a cathedral has a semi-spherical form (half of a sphere). If restoring the paint on the surface of the dome costs $125 per m2, what is the radius of the dome if the total cost of restoration is $314,159.27? Round your answer to the nearest whole number.
( Again He gives us the answer which is 10 cm but he hasn't showed us to work it :/ )

- Janine is planning on creating a water-based centerpiece for each of the tables at her wedding reception. She has already purchased a cylinder vase for each table. The radius of each vase is 8 cm and the height is 20 cm. She intends to fill each vase half way with water then add a variety of flowers to make it pretty. How many tables are at Janine's reception if she uses 70,371.68 cm3 of water?

hayharbr · Answer

60º is 1/6 of a full circle so 12.1 inches is 1/6 of the whole crust (circumference).  So C = 13.1 • 6 = 78.6 in.
And since C = π • d, 78.6 = π d making d = 78.6 ÷ π which rounds to the given answer.

Surface area of a sphere is 4 π r^2 so for a hemisphere it's half of that, 2 π r^2.
314,159.27 ÷ 125 = 2513.27 square meters  so you know
2 π r^2 = 2513.27
divide by 2π to get r^2 = 400 which makes r = √400 or 20 meters.. Uh oh.

Volume of cylinder = π r^2 h so for each vase that's π • 64 • 10
so see what that is then divide 70,371.68 by the answer

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how to solve these geometry problems? please help?

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