How much material should be ordered?

Question

A manufacturer has an order for 20,000 megaphones. The megaphones, conical in shape, are to be 2in. in diameter at the smaller end, 8in. in diameter at the other end, and 1ft. long. If 10 percent of the material used in manufacturing them will be wasted, how much material should be ordered?

(pls. show your solution)

(thanks...)

Answer 1

Surface Area of a cone:

A= Pi x (D+d) x L / 2

D=8in

d=2in

L=12in

So A = 188.49in^2 per cone

188.49 x 20,000 = 3769911.184 in^2 for 20,000 cones

110/100 x 3769911.184 = 4146902.303 in^2 including 10% wastage.