### AREA OF CIRCLE LESSON NOTE AND LESSON PLAN FOR PRIMARY AND SECONDARY SCHOOLS AND HIGH SCHOOLS

Days
W.A..L.T:
Content
Starter
Class activities
Plenary
Homework

Monday
Meaning of circle and  parts of a circle

Resources
a cardboard with circle drawn on it

A circle is a perfect round plane.

Examples of circle are; coins, wheels, rings, tin tops and bottom of buckets.

Parts of a Circle.
Centre: the point at the middle of the circle.

Circumference: is the curved outer edge of the circle. (the distance round the circle ). It is the longest part of a circle.

Diameter: the line from a side through the centre to another side. It divides the circle to equal halves. Half of a diameter is a radius.

Radius: is any straight line drawn from the centre to the circumference.

Semi-circle: half of a circle.

Quadrant : is a quarter part of a circle.

Chord: a straight line joining two points on the circumference. ( a chord does not divide a circle into equal halves like the diameter)

Sector: is a region between two radii and the circumference.

Begin the lesson by drawing a circle on the board and asking them what shape it is.

Pupils should be able to mention at least 4 parts of a circle then give explanation on them.

Tuesday
Finding the Area of circle

The area of a circle is found by using the formula πr² ,  where π is pi with value as 22/ 7  or 3.142 and where r is the radius of the circle.

Example:
1. Find the area of the circle with radius 7cm. Take π a 22/7
Solution
Area = πr² = π  X r X r
= ( 22/7 X 7 X 7 ) cm²
= 154cm²
2. Find the area of a circle of diameter 7cm. Take pi as 22/7
solution
radius is half of a diameter 7/2cm = 3  cm
area = πr² = π X r X r
= (   22/7 X  3.5  X  3. 5) cm²
= 38.5 cm²

Start the lesson by stating the formula for finding the area of the circle

Pupils should be able  to calculate the area of the shaded portion of the shape given

Wednesday
Finding the radius of a circle.

If you are required to find the radius of a circle when the area and pi are given, the rule is ; change the formula for finding the area.
Area = πr²  ( divide both sides by  π )
A = πr²

Radius  =   (A/π)¹/² (square root both sides)

Example : find the radius of a circle whose area is 154 cm2 . takes π as 22/7

= 7cm²

Begin the lesson by doing the first example for them.

Pupils should be able to calculate the area of the given shape correctly.

Thursday
Finding the area of semi- circle

Example :  find the area of the semi - circle with radius 7cm.Take π as 22/7.

Solution :
Area of semi- circle =  πr²/2
= (   22/7 X 7  X 7  )/2 cm²
=19.25 cm²

Begin the lesson by doing the first example for them.

Pupils should be able to calculate the area of the given shape correctly.