2 Surface Area What does it mean to you? Does it have anything to do with what is in the inside of the prism?VOLUME (not surface area) is the amount a shape can hold inside.Surface area is found by finding the area of the circle and the area around the cylinder and adding it together.
3 Surface Area of Cylinders What is area?The amount of square units that will COVER a shape.How will the answer be labeled?Units2 because it is area!
4 SURFACE AREA of a CYLINDER. Imagine that you can open up a cylinder like soYou can see that the surface is made up of two circles and a rectangle.The length of the rectangle is the same as the circumference of the circle!
5 EXAMPLE: Round to the nearest TENTH. Top or bottom circleA = πr²A = π(3.1)²A = π(9.61)A = 30.2 cm²RectangleC = length The length is the same as the CircumferenceC = π d C = π(6.2) C = 19.5 cmNow the areaA = lw A = 19.5(12) A = 234 cm²Now add:=SA = in²
6 2πr = πd SA = 2πr² + πd ·h This could be written a different way. A = πr² (one circle)This is the area of the top and the bottom circles.2πr = πdSo this formula could be written:SA = 2πr² + πd ·h
7 There is also a formula to find surface area of a cylinder. Some people find this way easier:SA = 2πrh + 2πr²SA = 2π(3.1)(12) + 2π(3.1)² SA = 2π (37.2) + 2π(9.61) SA = π(74.4) + π(19.2) SA =SA = in²The answers are REALLY close, but not exactly the same. That’s because we rounded in the problem.