The circumference of the top rim of the cone-shaped paper cup is 7.17 inches. Find the least amount of paper that can form the cone-shaped cup. (Round your answer to two decimal places.

Answer 1

*I realized that I did not put the height (3.9in) in the question above.

I am not sure how I got this right on the quiz, but I did! :)
This is the steps I wrote:

C=7.17
r=3.58
pi*3.58*/pi*3.9
=3.58*3.9
=13.98 in^2

Please, could anyone show me the correct formula steps on how to get to the correct work shown. I am still not entirely sure how I even came up with this.

Answer 2

lateral area of a cone of radius r and slant height s is
A = πrs = πr√(r^2+h^2)
since C = 2πr,
A = π(C/2π)√((C/2π)^2+h^2) = C/4π √(C^2 + (2πh)^2)

The formulas you used were
r = C/2
A = rh
I cannot see how it was even close