You have 9 gallons of lemonade to sell. You use a cone-shaped cups that are

10 centimeters in diameter and 12 centimeters tall. Each customer uses one paper cup. How many paper cups will you need if you sell all of the lemonade? (I gal is approximately 3785 cm cubed)

Volumen, V, of a cone: V = (1/3). π. (r^2). h

r = 10cm/2 = 5cm

h = 12

V = (1/3).π. (5cm) ^2.12cm = 314.16 cm^3

9 gallons = 9*3785 cm^2 = 34,065 cm^3

# paper cups = 34,065 cm^3 / 314.16 cm^3/cup = 108.43 cups

May be 108 cups is enough but if you want to be sure have 109 cups. Of course you do not have enough lemonade to fill completely 109 cups.