Presentation on theme: "Finding Area of Triangles and Parallelograms"— Presentation transcript:
1Finding Area of Triangles and Parallelograms The Rectangle MethodFinding Area of Triangles and Parallelograms
2A 30 Second Look-See Find something in the room shaped like: a hexagonal prisma cylindera quadranglea cubeA 30 Second Look-See
3Math Journal page 315 Read the top of page 315 Your job will be to think of ways to find the areas of the triangles – I am not interested in the answer.I am interested in the methods youand your partner discover.Math Journal page 315
4This is called the rectangle method because rectangles are used to surround the figure or parts of the figure. All of the areas that are calculated are either areas of rectangles or of triangular halves of rectangular regions.Rectangle Method
18Review your work Return to page 315. Find the area of triangle #1 by splitting the triangle into two right triangles. Use the add the parts method to find the area of the complete triangle.Review your work
19To find the area, draw two right angles around the triangle to create a rectangle.
20Find the area of the yellow and blue triangles Find the area of the yellow and blue triangles. Use the rectangle method mentally.
217 ½ units5 unitsFind the area of the yellow and blue triangles. Use the rectangle method mentally.
22The sum of the yellow and blue triangles is 12 ½ units.
23To find the area of the red triangle, find the area of the rectangle and subtract the 12 ½ units of the blue and yellow triangles.The difference will be the area of the red triangle.
2415 units – 12 ½ units = 2 ½ units.If the yellow triangle is 7 ½ units , and the blue triangle is 5 units, does it make sense that the red triangle is 2 ½ units?
33Review your work Return to page 315. Find the area of triangle #3 by splitting the parallelogram into two right triangles and a rectangle. Use the add the parts method to find the area of the complete parallelogram.Review your work
34Practice with a Partner Math Journal page 316Practice with a Partner