2. 1.3 Using Formulas Geometry

3. Perimeter Measures the distance around the edge of any flat object. To find the perimeter of any figure, ADD the lengths of its sides.

4. What is a rectangle? A rectangle has:  4 sides  4 square corners or right angles  Opposite sides are of equal lengths  Opposite sides are directly across from each other

5. To find the perimeter of a rectangle: 18 15 Use the formula P= 2 x length + 2 x width P= 2 x 18 + 2 x 15 P= 36 + 30= 66 Or ……. You can always add the sides. P= 18 + 18 +15 +15= 66

6. To find the perimeter of a rectangle: 18 15 Use the formula P= 2 x length + 2 x width P= 2 x 18 + 2 x 15 P= 36 + 30= 66 Or ……. You can always add the sides. P= 18 + 18 +15 +15= 66

7. The area of a shape is a measure of how much surface the shape takes up. Area For example, which of these rugs covers a larger surface? Rug A Rug B Rug C

8. Area of a rectangle Area is measured in square units. For example, we can use mm 2, cm 2, m 2 or km 2. The 2 tells us that there are two dimensions, length and width. We can find the area of a rectangle by multiplying the length and the width of the rectangle together. length, l width, w Area of a rectangle = length × width = lw

9. Area of a rectangle What is the area of this rectangle? 8 cm 4 cm Area of a rectangle = lw = 8 cm × 4 cm = 32 cm 2

10. A Real Life Example Seth is putting carpet in a bedroom that measures 14 ft by 12 ft. How many square feet of carpet does Seth need? – What do you know? The dimensions of the room is 14 ft by 12 ft. – l = 14 ft – w = 12 ft A = l x w – A = 14 ft x 12 ft – A = 168 ft 2 Seth needs 168 ft 2 of carpet.

11. Practice