of Cylinders 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. 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! SURFACE AREA of a CYLINDER. Imagine that you can open up a cylinder like so You 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! EXAMPLE: Round to the nearest TENTH. Top or bottom circle Rectangle A = πr² C = length The length is the same as the Circumference A = π(3.1)² A = π(9.61) A = 30.2 cm² Now add: 30.2 + 30.2 + 234 = SA = 294.4 in² C=πd C = π(6.2) C = 19.5 cm Now the area A = lw A = 19.5(12) A = 234 cm² This could be written a different way. 2πr = πd So this formula could be written: SA = 2πr² + πd ·h A = πr² (one circle) This is the area of the top and the bottom circles. There is also a formula to find surface area of a cylinder. Some people find this way easier: SA = 2πrh + 2πr² SA = 2π(3.1)(12) + 2π(3.1)² SA = 2π (37.2) + 2π(9.61) SA = π(74.4) + π(19.2) SA = 233.7 + 60.4 SA = 294.1 in² The answers are REALLY close, but not exactly the same. That’s because we rounded in the problem. Now It’s YOUR Turn! I think I can! I think I can! I think I can! I think I can! I think I can! I think I can!