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AREA OF SHAPES

CONTENT

  1. Area of a Circle
  2. Area of a Triangle
  3. Area of a Square
  4. Area of a Rectangle
  5. Area of a Parallelogram
  6. Area of a Trapezium
  7. Area of Irregular Shapes

 

Area of a Circle

Area of a circle \(= πr^2\)

Where \(π = \frac{22}{7}\)

Area of a circle - Diameter

Diameter \(= 2r\), where \(r = radius\)

Example: 

1. Find the area of a circle whose radius is \(3\frac{1}{2}m\). (Take \(π\) to be \(\frac{22}{7}\))

Solution:

Area of a circle \(= πr^2\)

\(\frac{22}{7} × (3 \frac{1}{2})^2 \\= \frac{22}{7} × \frac{7}{2} × \frac{7}{2} \\ = \frac{11×7}{2} \\ = \frac{77}{2}m^2 = 38.5m^2\)

2. The area of a circle is \(126.5cm^2\). Find its radius correct to \(2\) decimal places.

Solution:

Area of circle \(= πr^2\)

\(126.5cm^2 = \frac{22}{7} r^2 \\ \frac{253}{2} = \frac{22}{7} r^2 \\ 253 × 7 = 22 × 2 × r^2 \\ r^2 = \frac{161}{4} \\ r = \sqrt{\frac{161}{4}} \\ r = \frac{12.689}{2} \\ r = 6.345 \\ r = 6.35 (2 d.p.) \)

 

Area of a Triangle

Any diagonal of a rectangle divided into two equal right-angled triangles forms a right-angled triangle.

Lesson tags: JSS1 Mathematics, JSS1 Mathematics Evaluation Questions, JSS1 Mathematics Evaluation Questions Third Term, JSS1 Mathematics Objective Questions, JSS1 Mathematics Objective Questions Third Term, JSS1 Mathematics Third Term, Mathematics Lesson Notes, Mathematics Objective Questions
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