In this chapter, you will revise how to calculate the perimeter and area of squares, rectangles, triangles and circles. The perimeter of a shape is the distance all the way around the sides of the shape. The area of a shape is the flat space inside the shape. You will also learn how to calculate the areas of parallelograms, rhombi, kites and trapeziums, as well as investigate the effect on the perimeter and area of a shape when its dimensions are doubled.
Figure | Perimeter | Area | Number of 1 cm (times) 1 cm squares |
A | |||
B | |||
C | |||
D | |||
E | |||
F | |||
G | |||
H |
- Write down, without counting, the total number of squares that form this rectangle, including those that are hidden. Explain your reasoning.
- What is the area of the rectangle, including the white part?
- We can calculate the area of the room by dividing the floor into two rectangles, as shown in the diagram on the right below. Area of the room = Area of yellow rectangle + Area of red rectangle(= (l times b) + (l times b) = (14 times 9) + (15 times 8)= 126 + 120= 246 text{ m}^{2})
- The yellow part of the room has a wooden floor and the red part is carpeted. What is the area of the wooden floor? What is the area of the carpet?
- Calculate the area of the room using two different shapes. Draw a sketch.
- Perimeter (= 2 times (l + b) )
- Perimeter ( = l + b + l + b )
- Perimeter ( = 2l + 2b )
- Perimeter ( = l + b )
Kite Compositor 1 9 7 Cm Equals
The following are important formulae to remember:
- (d = 2 pi r) and (r= frac{1}{2}d)
- Circumference of a circle ((c) = 2 pi r )
- Area of a circle ( (A) = pi r^{2})
- A circle with a radius of 5 m
- A circle with a diameter of 18 mm
- a circumference of 53 cm
- a circumference of 206 mm
- an area of 200 m2
- an area of 1 000 m2
Remember:
1 cm = 10 mm 1 mm = 0,1 cm
1 m = 100 cm 1 cm = 0,01 m
1 km = 1 000 m 1 m = 0,001 km
- 34 cm = ..... mm
- 501 m = ..... km
- 226 m = ..... cm
- 0,58 km = ..... m
- 1,9 cm = ..... mm
- 73 mm = ..... cm
- 924 mm = ..... m
- 32,23 km = ..... m
1 cm (times) 1 cm
=0.01 m (times) 0.01 m
=0.0001 m2Example:
Convert 50 cm2to m2
1 cm2 = 0,0001 m2
Kite Compositor 1 9 7 Cm Berapa
50 cm= 0,005 m2Convert to cm2:
- 650 mm2
- 1 200 mm2
- 18 m2
- 0,045 m2
- 93 mm2
- 177 m2
- Convert 93 mm2 to m2
- Convert 0,017 km2 to m2
(therefore) Area of parallelogram = base (times) perp. height
We can use any side of the parallelogram as the base, but we must use the perpendicular height on the side we have chosen.
- Copy the parallelogram above into your exercise book.
- Using the shorter side as the base of the parallelogram, follow the steps above to derive the formula for the area of a parallelogram.
Area of a rhombus = length (times) perp. height