Defining and calculating MG 2 1 PERIMETER

Defining and calculating MG 2. 1: PERIMETER & AREA RECTANGLES, SQUARES, TRIANGLES, CIRCLES

Goal/Objective: • Students will be able to: Use formulas routinely for finding the perimeter and area of basic two- dimensional figures and the surface area and volume of basic threedimensional figures, including rectangles, parallelograms, trapezoids, squares, triangles, circles, prisms, and cylinders.

When your family puts up a new fence around your home, how will they know how much fencing they need? PERIMETER

Perimeter • The perimeter of a figure is the distance all the way around the figure.

Perimeter • The perimeter is found by adding the lengths of the sides together.

Find the perimeter of the figures. A. B. P = 24 m P = 21 cm

Perimeter of a Square • A square is a figure with 4 equal sides. • The perimeter can be found by adding all 4 sides together OR multiplying the side length by 4. So, P = 4 s

Find the perimeter of the squares using the formula P = 4 s. A. B. P = 36 m C. P = 28 in. D. P = 44 mm P = 20 cm

Perimeter of a Rectangle • A rectangle is a figure with 4 sides. Opposite sides are equal. • The perimeter can be found by adding all 4 sides together OR P = 2 w + 2 l

Find the perimeter of the rectangles using the formula P = 2 w + 2 l. B. A. P = 30 cm C. P = 28 m D. P = 54 mm P = 28 in.

If your parents want to put new carpet in your room, how will they know how much carpet to buy? AREA

Area • The area of a figure is the number of square units that cover the surface of the closed figure.

Area • A square unit is a unit that has 4 equal sides. • For metric units, we say “units squared”. Ex: centimeters squared or cm 2 • For U. S. Customary, we say “square units” Ex: square inches or sq. in.

Area • The area of a figure is found by finding how many square units it takes to cover its surface.

Area of a Square • The area of a square is found by finding how many square units it takes to cover its surface. • Area of a square is: A = s x s or A = s 2

Find the area of the squares using the formula A = s 2. B. A = 16 cm 2 A = 25 sq. in.

Area of a Rectangle • The area of a rectangle is found by finding how many square units it takes to cover its surface. • Area of a rectangle formula is: A = l x w

Find the area of the rectangles using the formula A = l x w. B. A = 24 cm 2 A = 77 sq. in.

Perimeter of a Triangle • Perimeter of Triangle= Sum of all sides P= 5 in + 7 in + 11 in P= 23 in 11 in 5 in 7 in

Area of a Triangle • Area of Triangle= 1/2 x (Base) x (Height) or bh/2

Circumference of a Circle

Example:

Formulas to Memorize! • • Perimeter of a polygon: add up the lengths of the sides Circumference of a circle: C=2 × π × r OR C= π × d Area of Rectangle: A= bh Area of Square: A=bh Area of a triangle A = ½ × b × h Volume of a rectangular solid: V=lwh Area of a Circle= A=πr 2