Lateral and surface areas of cones? There's an app for that. And if there isn't an app, there's a formula.
L = πrl
Our radius is 4 cm and our slant height is 5 cm. Plug those bad boys in.
L = π × 4 cm × 5 cm L = 62.8 cm2
That was easy enough. Surface area is just code for "add in the area of the circular base." For cones it is, anyway.
SA = L + πr2 SA = 62.8 cm2 + π × (4 cm)2 SA = 113.1 cm2
We have a soft spot in our hearts when it comes to cones. Well, soft serve, anyway.
Find the surface area of the solid.
This shape is a little weird. Before we calculate anything, we should come up with an overall surface area formula. The total surface area is the lateral area of a cylinder, and the two lateral areas of the cones.
SA = LCylinder + 2LCone
The lateral area of a cylinder is the circumference of the circle times the length of the cylinder. Circumference is two times the radius times our favorite dessert.