Chapter 13, Problem 2STP

To determine

Find the amount of paper needed to make the drinking cup.

Answer to Problem 2STP

F

Explanation of Solution

Given:

A machine is making steel washers by cutting out 10-millimeter circular disks from 34-millimeter circular disks .

  

Formula Used:

Lateral surface area of a cone with slant height l and radius r :

  $L=\pi rl$

Calculation:

The paper needed to make the conical glass is equal to the lateral surface area of the cone.

The radius, r of the cone is 2.5 cm

The height , h of the cone is 9 cm

Find the slant height , l of the cone :

  $l=\sqrt{r^2+h^2}=\sqrt{{2.5}^2+9^2}=\sqrt{6.25+81}=\sqrt{87.25}\approx 9.34cm$

So, the Lateral surface area of the cone is :

  $L=\pi rl\approx \pi (2.5)(9.34)\approx 73.4c{m}^2$

So, the correct option is F.