Question

Can someone please help me with this surface area of cylinder problem. I thought I had it but I didn't, I've gotten help from my teacher but I still don't get it. Please make it as simple as you can.

Answer 1

$SA=2 \pi r^2+2 \pi rh$

This is the formula for the surface area where r is the radius and h is the height. Finding the surface area will determine how much wrapping paper Jill needs (in inches squared).

The base measures 4 inches across. This means that the diameter is 4 inches. The radius is half the diameter (always). Thus, the radius is 2 inches. This means that r=2

The height is 10 inches. This means that h=10

The questions says to use 3.14 for π.

$SA=2(3.14)(2^2)+2(3.14)(2)(10)$

Use a calculator for this. Doing this by hand will take a painful amount of time.

$SA=150.72$

This was what I got from a calculator. I did not round at all.

The surface area is 150.72 inches squared. Thus, Jill will need 150.72 inches squared of wrapping paper. I hope this is what you needed to help you understand! :)