6th Grade Math Textbook, Progress

Area of Triangles and Parallelograms

13-10

Robin discovered the area formulas for triangles and

parallelograms using the area of a rectangle.

The base (b) and the height (h) of the

right triangle correspond to the length

and the width of the rectangle.

Area of Triangle: A

^12 
bh

Parallelogram The base (b) and the height (h) of the

parallelogram correspond to the length

and the width of the rectangle.

Area of Parallelogram: A
bh

A
bh

Right Triangle

Think

The area of the right triangle is

half the area of the rectangle.

Any side of a triangle can serve

as the base.

The height is the length of the

perpendicular segment from the

base to the opposite vertex.

Any side of a parallelogram can

serve as the base.

Think

The area of the parallelogram is

equal to the area of the rectangle.

height

base

height

base

height

base

h 5 3 cm

b 5 4 cm

w

A
^12 
bh

2

A


1

2 


4

1 
cm

3

1 
cm

1

A6 cm^2

h h = 3 cm

b = 5 cm

Abh

A5 cm3 cm

A15 cm^2

A



1

2 
bh

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