Question

To the nearest tenth of a square centimeter, what is the

surface area of the cone if the radius of its base is 5 cm and
its height is 12?
​

Answer 1

Answer: approximately 282.7 square cm

Work Shown:

SA = surface area of cone

SA = pi*r^2 + pi*r*sqrt(r^2 + h^2)

SA = pi*5^2 + pi*5*sqrt(5^2 + h^2) ... plug in r = 5

SA = pi*5^2 + pi*5*sqrt(5^2 + 12^2) ... plug in h = 12

SA = pi*25 + pi*5*sqrt(169)

SA = 25pi + 5pi*13

SA = 25pi + 65pi

SA = 90pi .... exact surface area in terms of pi

SA = 282.743338823081 .... see note below

SA = 282.7

note: this is the approximate surface area. I used the calculator's stored value of pi, rather than something like pi = 3.14; that way the surface area is as accurate as possible. Your teacher may want you to use pi = 3.14 though, which is why its a good idea to ask and clarify.