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Transcript of Surface Area
Question 1 (all, but not c, f) 20 mm 32 mm 15 mm 20 mm 25 mm Can we use a formula
for the SA of this shape?? Practice: Ex 3.2, page 103
Questions: 1c & f Solution: What shape is it? Cylinder... SA = 2 r + 2 rh 2 SA = 2 x x 5 + 2 x x 5 x 22 SA = 848.23 cm 2 2 Solution Divide it into its faces!! 20 mm 15 mm 25 mm 20 mm 32 mm 1 2 3 4 5 6 1 is a trapezium Area = a + b ________________ 2 x h A = (15 + 20)/2 x 20 A = 350 mm 2 2 is a rectangle Area = length x width Area = 20 x 32 Area = 640 mm 2 3 is a rectangle Area = 25 x 32 Area = 800 mm 2 4 is a rectangle Area = 15 x 32
Area = 480 mm 2 5 is a rectangle Area = 20 x 32
Area = 640 mm 2 6 is the same as 1 Area = 350 mm 2 Surface area of whole shape = 1 + 2 + 3 + 4 + 5 + 6 = 350 + 640 + 800 + 480 + 640 + 350 = 3260 mm 2 Is the sum of the area of all
the faces on a 3D shape. RULES What is Surface Area? The surface area of a rectangular prism and of a cube is the sum of the area of all 6 faces. What does sum mean? What kind of shapes are the faces on the shoebox? How do we find the area of rectangles? Is a rectangle 3D or 2D? A rectangular prism? Shoebox Activity! 1.Measure all faces of your shoebox.
2.Cut out colored construction paper to match these measurements.
3.Tape the paper onto your shoebox.
4. Calculate the surface area of your shoebox. Can you think of a formula to find the surface area of all rectangular prisms and cubes? 2(l x w) + 2(h x w) + 2(l x h) 3-2-1 3- Things you learned
2- Things that are still confusing
1- Object in the classroom that you could now find the surface area of. rectangular prism cube area add 1 40 2 3 4 5 6 40 48 48 30 30 40 40 30 30 48 48 236 ft^2 Rectangular Prism 8 5 6 Post it Activity!
#1- Yellow: Name three objects that are cylinders.
#2- Green: Why would we need to find the surface area of cylinders?
#3- Blue: Using what you know from finding the surface area of rectangular prisms and cubes, how do you think we should go about finding the surface area of a cylinder?
#4- Pink: Using what you know from finding the surface area of rectangular prisms and cubes, can you come up with a formula for finding the surface area of a cylinder?
On the back of your Post It, please explain the steps of how to find the surface area of any cylinder in paragraph form. You must use complete sentences. To find the surface area of a cylinder,
add the area of all surfaces. The curved surface makes a rectangle when unfolded.
A= L x W Area of a circle Area of a circle Since there are 2 circles that are congruent, multiply by 2 2 A= Height (h) Lengh: The circumference of the circle. C= d Surface Area
of a Cylinder = 2 + dh Cylinder: Surface Area Example 1 Example 2 Practice