What's in Unit 5?
Unit 5 covers
We can find the areas of triangles, parallelograms, and trapezoids.
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What is a parallelogram? Click to find out!
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Formulas
Parallelograms
A = b x h
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Triangles
A = 1/2 x b x h
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Trapezoids
A = 1/2 x (b1 + b2) x h
Steps to find Area of 2-D Shapes
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1. Decide: "what is the shape?"
2. Write that formula.
3. Rewrite the formula, replacing "b" with the base measurement and replacing "h" with the height measurement.
4. Follow the order of operations (PEMDAS, look at unit 3 if you need review)
5. Show your answer using square inches.
Ex. A = 34 square inches
A = 34 in^2
Practice Finding Area
Parallelograms:
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Triangles:
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Special Quadrilaterals
A parallelogram has two parallel pairs of opposite sides.
A rectangle has two pairs of opposite sides that are parallel, and four right angles. (It is also a parallelogram, since it has two pairs of parallel sides.)
A square has two pairs of parallel sides, four right angles, and all four sides are equal. It is also a rectangle and a parallelogram.
A rhombus is defined as a parallelogram with four equal sides. Is a rhombus always a rectangle? No, because a rhombus does not have to have 4 right angles.
Trapezoids only have one pair of parallel sides. It's a type of quadrilateral that is not a parallelogram.
Kites have two pairs of adjacent sides that are equal.
Steps to Find Irregular Figures
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1. Decompose, or split them, into familiar shapes (parallelograms, triangles or trapezoids).
2. Find the area of each part of the composite shape.
3. Add to find the total.
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Finding Areas of Irregular Figures
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2-D & 3-D Figures
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Fun "Real-World" Cross Sectional Commercial
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Describe the 2-D figures that result from slicing (cross-section of 3-D figures)
Steps to find Surface Area of Rectangular or Triangular Prisms:
1. Find the area of each face. (Use formula for each shape, either parallelogram or triangle.)
2. Add to find the total. (Remember you will have 6 faces for a rectangular prism and 5 faces for a triangular prism.)
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Finding surface area of a rectangular prism
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All about surface area interactive
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Finding surface area of triangular prism
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Finding Area of Triangular Prism
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Unit 5 Vocabulary
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Quadrilateral: a polygon with 4 sides.
Polygon: a closed figure with 3 or more sides that intersect at their ends.
Triangle: A polygon with three sides.
Right triangle: A triangle with exactly one right angle.
Area: the surface covered in a two-dimensional figure, measured in square units.
Parallelogram: a quadrilateral with opposite sides that are parallel.
Trapezoid: a quadrilateral that has only one pair of parallel sides.
Congruent: the same.
Composition: putting pieces together.
Decomposition: breaking into pieces.
Net: a flat shape which can be folded up into a 3D solid figure.
Surface area: the total area of the surfaces of a 3D solid figure.
Rectangular prism: a 3D figure with 6 rectangular faces.
Triangular prism: a 3D figure with 2 triangular faces and 3 rectangular faces.