Topics
Number System(Consolidating the Sense of Numberness)
Number System
Estimation
Ratio and Proportion
Algebra
Numbers in India and International System (With Comparison)
Geometry
Place Value
Mensuration
Natural Numbers and Whole Numbers (Including Patterns)
Data Handling
Negative Numbers and Integers
Number Line
HCF and LCM
Playing with Numbers
- Simplification of Brackets
- Finding Factors Using Rectangular Arrangements and Division
- Factors and Common Factors
- Multiples and Common Multiples
- Concept of Even and Odd Number
- Tests for Divisibility of Numbers
- Divisibility by 2
- Divisibility by 4
- Divisibility by 8
- Divisibility by 3
- Divisibility by 6
- Divisibility by 9
- Divisibility by 5
- Divisibility by 11
Sets
Ratio
Proportion (Including Word Problems)
Unitary Method
Fractions
- Concept of Fraction
- Types of Fractions
- Concept of Proper and Improper Fractions
- Concept of Mixed Fractions
- Like and Unlike Fraction
- Concept of Equivalent Fractions
- Conversion between Improper and Mixed fraction
- Conversion between Unlike and Like Fractions
- Simplest Form of a Fractions
- Comparing Fractions
- Addition of Fraction
- Subtraction of Fraction
- Multiplication of Fraction
- Division of Fractions
- Using Operator 'Of' with Multiplication and Division
- BODMAS Rule
- Problems Based on Fraction
Decimal Fractions
Percent (Percentage)
Idea of Speed, Distance and Time
Fundamental Concepts
Fundamental Operations (Related to Algebraic Expressions)
Substitution (Including Use of Brackets as Grouping Symbols)
Framing Algebraic Expressions (Including Evaluation)
Simple (Linear) Equations (Including Word Problems)
Fundamental Concepts
Angles (With Their Types)
Properties of Angles and Lines (Including Parallel Lines)
Triangles (Including Types, Properties and Constructions)
Quadrilateral
Polygons
The Circle
Symmetry (Including Constructions on Symmetry)
Recognition of Solids
Perimeter and Area of Plane Figures
Data Handling (Including Pictograph and Bar Graph)
Mean and Median
- Introduction
- Trapezium
- Isosceles Trapezium
- Parallelogram
- Rectangle
- Rhombus
- Square
- Example 1
- Example 2
- Example 3
- Key Points Summary
Introduction
A quadrilateral is a closed figure with four sides and four angles. Based on the relationships between its sides and angles, different types of quadrilaterals exist — such as trapezium, parallelogram, rectangle, rhombus, and square.
Understanding these shapes is essential because they form the basis for most of the structures and objects we encounter daily, from rectangles and squares to the less common parallelograms and trapeziums.
Trapezium

Has only ONE pair of parallel sides then ABCD is a trapezium.
Key Properties:
- Sum of angles = 360°
-
Co-interior angles = 180° (angles on the same side of parallel lines ∠A + ∠D = 180° and ∠B + ∠C = 180°)
Isosceles Trapezium

Non-parallel sides are equal is called an isosceles trapezium.
Key Properties:
- Non-parallel sides are equal:
AD = BC
-
Base angles are equal:
∠A = ∠B and ∠C = ∠D -
The diagonals are equal in length:
AC = BD -
The pairs of co-interior angles are supplementary:
∠A + ∠D = 180° and ∠B + ∠C = 180°
Parallelogram

Has TWO pairs of parallel sides (opposite sides face each other)
Key Properties:
-
Opposite sides are equal in length
AB = DC and AD = BC -
Opposite angles are equal
∠A = ∠C and ∠B = ∠D -
Adjacent angles add up to 180°
∠A + ∠B = 180° and ∠B + ∠C = 180°
∠C + ∠D = 180° and ∠D+ ∠A= 180° -
Diagonals bisect each other (cross at their midpoints)
OA = OC and OB = OD
Rectangle

ALL FOUR angles are 90°
Key Properties:
-
All angles = 90°
-
Opposite sides are equal
AB = DC,AD = BC -
Opposite sides are parallel
-
Diagonals are equal in length
AC = BD -
Diagonals bisect each other
OA = OC,OB = OD
Rhombus

A rhombus is a quadrilateral in which ALL SIDES are equal.
Key Properties:
-
All sides are equal
-
Opposite angles are equal.
-
Diagonals bisect each other at right angles (90°).
-
A parallelogram with equal adjacent sides.
Square

A square is a quadrilateral in which ALL SIDES are equal and each angle is 90°.
Key Properties:
-
All sides are equal
-
All angles are right angles
-
Diagonals are equal and bisect each other at right angles.
Example 1
Isosceles trapezium ABCD with ∠B 82°. find angles A, C and D.

Solution:
Steps:
- ∠A = ∠B = 82° (Base angles are equal)
∠C + ∠B = 180° => ∠C + 82° = 180° (Co-interior (same-side) angles on parallel lines are 180∘) - ∠C = 180° − 82° = 98°
- ∠D = ∠C = 98°
∴ ∠A = 82°, ∠C = 98° and ∠D = 98°.
Example 2
Each angle of a quadrilateral equals x. Show it’s a rectangle.

Solution:
Steps:
-
Sum of interior angles of any quadrilateral .
. -
x = `"360°"/"4"`
Conclusion: x = 90∘ and the figure is a rectangle.
Example 3
Rhombus ABCD, with a diagonal = AC and ∠ DAC = 30°. Find all the angles of the rhombus.
Solution:
Steps:
- ∴ ∠CAB = ∠DAC = 30° (diagonals bisect the angles at the vertex.)
==> ∠DAB = 30° + 30° = 60° - ∠BCD = ∠DAB = 60° (opposite angles are equal.)
- ∠DAB + ∠ABC = 180° (adjacent angles are supplementary).
⇒ 60° + ∠ABC = 180°
∠ABC = 180° − 60 = 120°
Also, ∠ADC = ∠ABC = 120°
∴ Required angles are 60°, 120°, 60° and 120°
Key Points Summary
| Quadrilateral | Parallel Sides | Sides Equal | Angles | Diagonals |
|---|---|---|---|---|
| Trapezium | One pair | Not equal | Co-interior angles = 180° | Not equal, don’t bisect |
| Isosceles Trapezium | One pair | Non-parallel sides equal | Base angles equal | Equal in length |
| Parallelogram | Two pairs | Opposite sides equal | Opposite angles equal | Bisect each other |
| Rectangle | Two pairs | Opposite sides equal | All 90° | Equal and bisect each other |
| Rhombus | Two pairs | All sides equal | Opposite angles equal | Bisect at 90° |
| Square | Two pairs | All sides equal | All 90° | Equal and bisect at 90° |



