Question

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

Answer 1

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.