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Measuring Area
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Area: The number of square units that can be contained on a surface. Imperial area units > Inches in 2 > Feet ft 2 > Yards yd 2
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Area can be found by multiplying the length by the width. Area = Length x Width A = l x w *This allows you to find the area inside a square or rectangle
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What is the area of this square? Length = 6 in width = 6 in Area = length x width Area = 6 in x 6 in Area = 36 in 2
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Find the length 4.5 ft 2 Find the width 1.5 ft 2 Use the formula for area A = l x w A = 4.5 ft x 1.5 ft A = 6.75 ft 2
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Length = 7 yd Width = 4 yd A = l x w A= 7 yd x 4 yd A= 28 yd 2
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To find the area of this shape we will need to think of two rectangles. This will let us use A = l x w
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Do the side with the squares first. The area of L-shaped figures is more difficult.
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A triangle can be though of as half of a square or rectangle. This means the same formula is used but we must half the value.
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You need to make sure you have the base and height correct.
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The base and the height must be perpendicular.
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Find the area of this triangle.
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Sometimes the base is given as two numbers and they must be added together.
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The true height of a triangle is usually inside the figure. In some cases it can be outside the triangle. If this happens it will be marked like this…
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Complete the practice sheet on finding the area of triangles. I would like you to hand this sheet in when you are finished. Remember to put the proper area units with the answers.
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Finding the area of a circle requires this formula. This formula has no variations. The radius must be used to solve correctly. A = πr 2
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If diameter is given we must divide it by two. This will give us the radius for the area formula.
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Find the area of a circle which has a radius of 11.6 cm.
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A circle has a radius of 4.2 m. Find the area of the circle.
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The diameter of a circle was found to be 24.6 in. What is the area of the circle?
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If you did not complete the area of a triangle worksheet you should complete that first and hand it in. Complete both worksheets on the circle. The second sheet on circles is being handed in.
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We know how to find the area of squares, rectangles, triangles, and circles. If a new shape is made out of only these shapes we know, then we can find the area of that shape as well. The trick is to break the composite shape into shapes you can deal with.
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What is the area of this shape?
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First determine what shapes are contained in the compound shape. Find the measurements for each part you will need. Write down the formula for each piece and solve. Add all the small areas together.
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Many 3D objects contain shapes we can find the area of. This means we can find the total surface area of those objects as well.
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Another very common object we need to be able to find the area of is the cylinder.
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Area of a rectangular Prism SA = 2 ( lw + lh + wh ) Area of a cylinder SA = 2πr 2 + 2πrh
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Find the total surface area of a box with length 5 ft, width 3 ft, and height 2 feet? **(It is a good idea to draw the object)**
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A shipping container has the following dimensions. Height 3.5m, length 12.8m, and a width of 3.0m. A painter needs to know the surface area of the container. Calculate the surface area of the container.
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Complete the worksheet on Surface area of a rectangle prism.
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Cylinders are basically circles with a height component to them. The thing to be aware of with circles is the formula uses the radius (r). If you are given the diameter, you must change it to radius before putting it in the formula.
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Don’t forget!!
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An oil barrel is 33.5 in tall. It has a diameter of 22.5 in. Sketch the barrel and calculate the surface area of the barrel. (SA = 2πr 2 + 2πrh)
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A milk holding container is shaped like a cylinder. If the tank is 3.25 m tall and has a radius of 2.5 m, what is the total surface area of the tank? (SA = 2πr 2 + 2πrh)
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A company manufactures aluminum beverage cans in two sizes: Can “A” has a diameter of 2.5in and a height of 4.5in. Can “B” has a diameter of 3in and a height of 3in. Which can requires more aluminum to make? (SA = 2πr 2 + 2πrh) We need to compare the surface area of each can!
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