188.4 square inches
The given hats is in form of a cone. The lateral area of the hat (we use lateral hat since party hat has no base) is given as:
[tex]L=\pi rl[/tex]where:
r is the radius of the hat
l is the slant height
Given the following parameters;
r = 4inches
l = 5inches
Determine the lateral area of a hat
[tex]\begin{gathered} L=3.14\times4\times5 \\ L=62.8sq.in \end{gathered}[/tex]Since there are three party hats, the lateral surface area of the three hats will be:
[tex]\begin{gathered} L=3(62.8) \\ L=188.4sq.in \end{gathered}[/tex]Hence the amount of paper needed for the three hats is 188.4 square inches