ACT Math 2.5 Plane Geometry
ACT Math Plane Geometry Drill 2, Problem 5. What is the surface area of a rigid circular cone with diameter = 10 and height = 12?
|ACT Math||Plane Geometry|
|ACT Mathematics||Plane Geometry|
|Area and Volume||Area|
|Foreign Language||Arabic Subtitled|
|Plane Geometry||Surface area|
|Product Type||ACT Math|
surface area equals pi times r times the square root of the quantity radius squared plus height squared.
Well, they give us the height. Now we need the diameter to tell us what the radius is;
...and in a circle, here is the diameter -- the radius is just half of it. So if diameter is 10
half is 5.
Now just plug in the numbers.
It's pi times 5 times the square root quantity of 5 squared plus 12 squared which simplifies to
5 pi times the square root quantity 25 plus 144 or 169 -- and ooh magic number --
169 should trigger a bell in your head.
It is 13 squared.
So we have 5 times pi times 13 -- 5 times 13 is 65 so the answer is 65 pi.