Debbie wants to decorate 3 lampshade. the diameter of the top of each lampshade is 8 inches and the diameter of the bottom is 12 inches.hiw much fridge will she need to buy?

The cost is minimized for

 and then and the ratio height / radius = 2.3

Step-by-step explanation:

When you solve these kind of problems you always need to ask yourself what am I minimizing or maximizing, for this case you need to minimize the cost function.

Suppose that the bottom of your drum has a radius and a height and a height then the are of the circle at the bottom would be

And the area of the sides would be given by

According to what they say the cost of the sides is 2$ per square meter and the cost of the bottom is 3$ per square meter.

So the cost would be given by this function.

Cost =

But they mention that the volume = 2 cubic meters. On the other hand

Volume = = 2   if we replace on Cost we get that

When you find the derivative of that and equal to zero you will find that the the cost is minimized for

 and then and the ratio height / radius = 2.3