Presentation on theme: "Finding Area of Triangles and Parallelograms"— Presentation transcript:
1 Finding Area of Triangles and Parallelograms The Rectangle MethodFinding Area of Triangles and Parallelograms
2 A 30 Second Look-See Find something in the room shaped like: a hexagonal prisma cylindera quadranglea cubeA 30 Second Look-See
3 Math 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
4 This 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
18 Review 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
19 To find the area, draw two right angles around the triangle to create a rectangle.
20 Find the area of the yellow and blue triangles Find the area of the yellow and blue triangles. Use the rectangle method mentally.
21 7 ½ units5 unitsFind the area of the yellow and blue triangles. Use the rectangle method mentally.
22 The sum of the yellow and blue triangles is 12 ½ units.
23 To 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.
24 15 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?
33 Review 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
34 Practice with a Partner Math Journal page 316Practice with a Partner