mg 2.1: perimeter & area rectangles, squares, triangles, circles defining and calculating

MG 2.1: PERIMETER & AREA RECTANGLES, SQUARES, TRIANGLES, CIRCLES

Defining and calculating

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 three- dimensional 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 mP = 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 = 4s

Find the perimeter of the squares using the formula P = 4s .

A.

B.

D.C.

P = 36 m P = 28 in.

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 = 2w + 2l

Find the perimeter of the rectangles using the formula P =

2w + 2l.A.

B.

D.

C.

P = 30 cm

P = 28 m

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 cm2

• 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 = s2

Find the area of the squares using the formula A = s2.

A.

B.

A = 16 cm2 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.

A.

B.

A = 24 cm2 A = 77 sq. in.

Perimeter of a Triangle

• Perimeter of Triangle= Sum of all sidesP= 5 in + 7in + 11 in

P= 23 in

11in

7in

5 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=πr2