# 1.3 Using Formulas Geometry Perimeter Measures the distance around the edge of any flat object. To find the perimeter of any figure, ADD the lengths.

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1.3 Using Formulas Geometry

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

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

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

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

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

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

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

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.

Practice

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