AREAS AND PERIMETERS

TRIANGLE SQUARE RECTANGLE

RHOMBUS TRAPEZIUM CIRCLE

TRIANGLE

areaarea perimeterperimeter

Base times height

over two

Add the three sides up

heightheight

h h

basebaseb b

area = 2

hb

3cm

4cm

3cm

2cm

EXAMPLE

262

34cm

232

32cm

b

ac

Perimeter = a + b + c

EXAMPLE

5cm

3cm4cm

3 + 5 + 4 = 12cm

areaarea perimeterperimeter

Side times side =side squared

Addition of the sides

SQUARE

Area = 2lll

22 25555 cm

l

l

It must be the same shape as the rectangle

Área = a·ba

b

5cm

5 cm

EXAMPLE

Perimeter = l + l + l + l = 4·l

l

l

3cm

3cm

4·3 = 12cm

EXAMPLE

areaarea perimeterperimeter

The longest side times the

shortest side

Addition of the sides

Press here to see the development of the

area formula

Press here to see the development of the perimeter formula

RECTANGLE

Area = a · b

21535 cm

b

a

If the sides were equal, it would be useful for

the square

Area = a·ba

b

3cm

5cm

EXAMPLE

Perimeter = a + b + a + b = 2·a + 2·b = 2·(a+b)

b

a

3cm

5cm

2·(5+3) = 16cm

E XA M P L E

areaarea perimeterperimeter

The longest diagonal times the shortest

diagonal divided by two

Addition of the sides

Press here to see the development of the

area formula

Press here to see the development of the perimeter formula

RHOMBUS

Example

Area = 2

dD

2202

58cm

D

d

8cm

5cm

E XAMPLE

Perimeter = l + l + l + l = 4·l

4·3 = 12cm

l

l

3cm

3cm

areaarea perimeterperimeter

Semiaddition of the bases

times the height

Addition of the sides

Press here to see the development of the

area formula

Press here to see the development of the perimeter formula

TRAPEZIUM

E XAMPLE

If the bases were equal, we would have a rectangle.

Area = a·ba

b

h

heightheight

b1

b2

basesbases

5cm

3cm

2cm

Area =

hbb

2

21

2822

35cm

EXAMPLE

Perimeter = b1 + c + b2 + a

7+3+5+4 = 19cm

a

b2

b1

c4cm

5cm

7cm

3cm

circlecircle circumferencecircumference

times the radium squared

(pai)(3.14159...)

Press here to see the developmet of the

area formula

Press here to see the development of the perimeter formula

Diameter times

CIRCUMFERENCE AND CERCLE

Will it be a circle or will it be a circumference?

Neither one nor the other

And then, what is it?

Is it possible I don’t know what a sphere is?

A beach ball

E XAMPLE

Area = 2r

r

10cm

22 159,31410 cm

I t is always an approximate value

E XA M P L E

Length = r2

r

5cm

cm4159,3152

It is always an approximate value