Transcript Primary Mathematics: Building the Concept of AREA in Grades 4

Primary Mathematics:
Building the Concept of
AREA
in Grades 4 through 7.
Before we can talk about
AREA
we need to build the
concept of
Square Unit
The total weight of Peter, David, and Henry is 123 kg.
Peter is 15 kg heavier than David. David is 3 kg
lighter than Henry. Find Henry’s weight.
Peter
15kg
123 kg
David
Henry
3kg
As we work with the BAR MODEL in
grades 3 and 4 we want to emphasize
the concept of UNIT.
Peter
UNIT
David
UNIT
Henry
UNIT
15kg
3kg
PM 4A
1 Unit
One SQUARE Unit
1 Unit
PM 4A
Find the AREA of the
RECTANGLE.
I count the square
units covered by each
rectangle to find its
area
A square centimeter
is a unit of area.
PM 4A
Width = 3 cm
Find the AREA of the
RECTANGLE.
I multiply the length
and width of each
rectangle to find its
area
Length = 4 cm
The AREA of the RECTANGLE is 12 square centimeters.
PM 4A
2 cm
The AREA of the RECTANGLE is
8 square centimeters.
4 cm
Area = 4 x 2
Area = 2 x 4
PM 4A
We can use the
symbols A, l, and w to
represent area, length,
and width.
A= l x w
w= 4cm
l = 6cm
A= 6 x 4 square cm
The area of the rectangle is 24 square cm
1 inch
PM 4A
1 inch
One SQUARE inch
PM 4A
Other units of area include:
meter
mile
foot
11yard
Square meter ( m 2 )
2
Square foot ( ft )
111meter
yard
foot
mile
Square yard ( yd 2)
2
Square mile ( mi )
PM 4A
l = 42 cm
w = 34 cm
A=?
The area of a rectangle is 24 square inches. PM 4A
If the length of the rectangle is 6 inches, find its width.
?
6 inches
The width of the rectangle is 4 inches.
The figure is made up of two rectangles.
Find the area of the figure.
PM 4A
30 feet
8 feet
Area = 30 x 8
Area = 240 square feet
20 feet
12 feet
Area = 240 + 240
Area= 480 square feet
Area = 20 x 12
Area = 240 square feet
20 feet
The figure is made up of two rectangles.
Find the area of the figure.
PM 4A
30 feet
8 feet
Area = 10 x 8
Area = 80 square feet
Area = 20 x 20
Area = 400 square feet
20 feet
10 feet
Area = 80 + 400
20 feet
The area of the figure is 480 square feet.
PM 5A
Find the area of the figure.
PM 5A
What is the area of the triangle?
2 cm
8 cm
The area of the triangle is 8 square cm
What is the area of the triangle?
2 cm
8 cm
The area of the triangle is 8 square cm
Area of the rectangle = 20 square units
Area of one triangle = 7.5 square units
Area of the second triangle = 2.5 square units
Area of the original triangle = 10 square units
PM 5A
Find the area of the figure.
Area = (2.5 + 35 + 2.5) square units
Area = 40 square units
Find the area of the grey region.
Area of the rectangle
Minus
Area of the circle
Find the area of the grey region.