Area of Polygons------------------------.ppt
- 2. Area of Rectangles 9 in. Length 3 in. Width The area of an object is how many squares it would take to cover the inside of an object. Area is always measured in square units. For a rectangle, this can be calculated by multiplying the length times the width. 2 9 3 27 in. A l w A A
- 3. Area of Squares 3 in. Side 3 in. Side A square is a special type of rectangle. A square has all sides the same length. Therefore, we do not need a length and a width. We can simply call them sides. The area of a square can be calculated by multiplying side by side…or side squared. 2 2 3 3 9 in. A s A A
- 4. 7 cm Area of Parallelograms Therefore, the area of parallelogram is same as a rectangle. We know the area of a rectangle is length times width. 4 cm We can take the rectangle, cut off one side, and add it to the other side. The area must still be 4 times 7 or 28 cm.2 .
- 5. Area of Parallelograms For a parallelogram, we use the terms base and height. Remember, the height is measured straight up and down (like the doctor measures your height!). Therefore, the height of this parallelogram is 4 cm., not 5 cm. 7 cm 5 cm 4 cm 2 7 4 28 cm. A b h A A The area of a parallelogram can be found by multiplying the base times the height.
- 6. Area of Triangles 7 cm 4 cm Starting with our same parallelogram, we can cut it in half to form two triangles. Half the area ended up in each triangle. 7 cm 4 cm Notice that the base and the height of the new triangle are the same as in the parallelogram. The area of a triangle can be found by multiplying the base times the height and then dividing by two. 2 2 7 4 2 14 cm. b h A A A
- 7. Area of Trapezoids 7 cm. 4 cm A trapezoid is very similar to a parallelogram as well. Notice that you can flip (or reflect) the left side and it now becomes a trapezoid with the same area as the parallelogram. 2 cm. The area of this trapezoid must still be 28 cm.2 . Notice that the bottom base is now 2 cm. shorter and the top base is now 2 cm. longer. 5 cm. 9 cm.