The lateral area of a cone is half the product of the slant height and the circumference. Of course, the circumference is pi times the diameter.
A = (1/2)·π·d·s
A = (1/2)·3.14·(3 in)·(6 in)
A = 28.26 in²
About 28.26 in² of paper are needed to make the cone.
