Question

Given the figure below, how much paper is needed to make the drinking cup to the nearest square inch?

Answer 1

To find this, we need to find the Surface area of the lateral surface of the cone (without the circle base).

`LSA _(cone) = \pi rl`
Now we just need to plug what we know into the equation

`r=1.5 \\l=4`

`LSA _(cone) = \pi (1.5)(4) \\LSA_(cone)= 6\pi`
Wither you can keep your answer in pi or take it out of pi, depending on what the requirements are.
To take it out of pi you need to multiply 6 by pi (remembering to use 3.14 as pi in most cases since that is what is generally accepted on tests and exams).

`6 \pi = 6(3.14)= 18.84`
Then rounding to the nearest square inch which would mean that the amount of paper needed is =19in²