Bob's Barricades rents orange plastic cones to use as barricades in road construction. Each cone is 24 inches high with a diameter of 14 inches. A gallon of orange paint will cover approximately 400 square feet. About how many whole gallons of paint will Barb need to paint the lateral sides only of the 300 cones.

2 answers

I will assume that we paint only the lateral surface of each cone
SA = πrs, where s is the slant height

http://math.about.com/od/formulas/ss/surfaceareavol_2.htm

so s^2 = 7^2 + 24^2
s = √625 = 25

So each cone has a lateral SA of π(7)(25) or 175π inches^2
300 cones have 52500π inch^2
number of gallons of paint
= 52500π/400
=412.33
but we can't buy a partial gallon, so
413 gallons are needed

check my arithmetic
It is 3 gallons