Plane Shapes.

Mathematics for JS 1 3^RD TERM.

Week1 and 2.

Theme: Mensuration and Geometry.

Plane Shapes.

Performance Objectives.

Student should be able to

1. State the similarities and differences between

(a) Square and rectangle,

(b)Triangle and Trapezium,

(c) Parallelogram and circle.

2. Find the area of plane shapes.
3. Find the area of real-life objects.

Content.

Week 1.

Square and Rectangle.

         Rectangle                                               Square

 

 

Similarities.

1. Both have 4 sides.
2. They both have 4 angles.
3. Each angle equals 90°.
4. Sum of interior angles are the same.

Differences.

1. All sides of a square are equal, in rectangle two opposites sides are equal.
2. Rectangle has 2 lines of symmetry while a square has 4 lines of symmetry.
3. In a square the diagonal bisects at right angle triangle, while in a rectangle the diagonals bisect at acute and obtuse angles.

Triangle and Trapezium.

 

       

 

     Similarities.

1. Both have types called isosceles(opposite sides are equal).
2. Both have base angles.

Differences.

1. There are their types of triangle (equilateral triangles where all sides and angles are equal, Isosceles triangle where two base angles and opposite sides are equal, a scalene triangle where no side or angle is equal), while trapezium is of two types.
2. Trapezium has parallel sides as bases and non-parallel leg.
3. triangle has only one line of symmetry.

Parallelogram And Circle.

 

 

 

Similarities.

1. The sum of interior angles are the same.

Differences.

1. All sides of a parallelogram are parallel, while a circle has a round shape.

Area.

Area of plane shapes is a measure of the amount of surface surface it covers or occupies.

Area is measured in square units.

Example 1.Find the area of a rectangle of length 250cm and width 200cm.

Area of a rectangle =Lx B or(W)

(250 X200)cm²

=50,000cm².

Example 2:Calculate the area of a parallelogram with the base 8cm and height 9cm

Area of parallelogram =base X height.

8cmX9cm

=72cm.

 

PERIOD 2.

Area of Triangles and trapezium.

Example1: Calculate the area of a triangle with base 5cm and height 4cm.

Area of a triangle =1/2 B x H.

=1/2X5X4

=2x5=10cm².

Example 2: The  parallel sides of trapezium of parallel sides 25cm and 35cm.If the area of the trapezium is 540cm²,find the distance between the parallel sides.

A=5(cm, h=?

Area of trapezium=1/2(a+b) xh

540=1/2(25+35)x h

540=1/2x60xh

540=30h

540/30=h

18cm=h.

Example 3: find the area of a circle with radius 12.5cm.

Area of a circle A=πr2

22÷7x12.5x12.5

=39.29cm².