Topics
Integers
- Natural Numbers
- Whole Numbers
- Negative and Positive Numbers
- Integers
- Representation of Integers on the Number Line
- Ordering of Integers
- Addition of Integers
- Subtraction of Integers
- Properties of Addition and Subtraction of Integers
- Multiplication of a Positive and a Negative Integers
- Multiplication of Two Negative Integers
- Product of Three Or More Negative Integers
- Closure Property of Multiplication of Integers
- Commutative Property of Multiplication of Integers
- Multiplication of Integers with Zero
- Multiplicative Identity of Integers
- Associative Property of Multiplication of Integers
- Distributive Property of Multiplication of Integers
- Making Multiplication Easier of Integers
- Division of Integers
- Properties of Division of Integers
Fractions and Decimals
- Concept of Fraction
- Types of Fractions
- Concept of Proper and Improper Fractions
- Concept of Mixed Fractions
- Concept of Equivalent Fractions
- Like and Unlike Fraction
- Comparing Fractions
- Addition of Fraction
- Subtraction of Fraction
- Multiplication of a Fraction by a Whole Number
- Using Operator 'Of' with Multiplication and Division
- Multiplication of Fraction
- Division of Fractions
- Concept of Reciprocals or Multiplicative Inverses
- Problems Based on Fraction
- The Decimal Number System
- Comparing Decimal Numbers
- Addition of Decimal Fraction
- Subtraction of Decimal Numbers
- Multiplication of Decimal Numbers
- Division of Decimal Numbers
- Problems Based on Decimal Numbers
Data Handling
Simple Equations
Lines and Angles
The Triangle and Its Properties
- Basic Concepts of Triangles
- Classification of Triangles based on Sides
- Classification of Triangles based on Angles
- Median of a Triangle
- Altitudes of a Triangle
- Exterior Angle of a Triangle and Its Property
- Some Special Types of Triangles - Equilateral and Isosceles Triangles
- Basic Properties of a Triangle
- Right-angled Triangles and Pythagoras Property
Comparing Quantities
- Ratio
- Concept of Equivalent Ratios
- Proportion
- Unitary Method
- Basic Concept of Percentage
- Estimation in Percentages
- Interpreting Percentages
- Conversion between Percentage and Fraction or Decimal
- Ratios to Percents
- Increase Or Decrease as Percent
- Basic Concepts of Profit and Loss
- Profit or Loss as a Percentage
- Calculation of Interest
Congruence of Triangles
- Similarity and Congruency of Figures
- Congruence Among Line Segments
- Congruence of Angles
- Congruence of Triangles
- Criteria for Congruence of Triangles
- Criteria for Similarity of Triangles
- SAS Congruence Criterion
- ASA Congruence Criterion
- RHS Congruence Criterion
- Exceptional Criteria for Congruence of Triangles
Rational Numbers
- Rational Numbers
- Equivalent Rational Number
- Positive and Negative Rational Numbers
- Rational Numbers on a Number Line
- Rational Numbers in Standard Form
- Comparison of Rational Numbers
- Rational Numbers Between Two Rational Numbers
- Addition of Rational Number
- Subtraction of Rational Number
- Multiplication of Rational Numbers
- Division of Rational Numbers
Perimeter and Area
- Basic Concepts in Mensuration
- Concept of Perimeter
- Perimeter of a Rectangle
- Perimeter of Squares
- Perimeter of Triangle
- Perimeter of Polygon
- Concept of Area
- Area of Square
- Area of Rectangle
- Triangles as Parts of Rectangles and Square
- Generalising for Other Congruent Parts of Rectangles
- Area of a Parallelogram
- Area of a Triangle
- Circumference of a Circle
- Area of Circle
- Conversion of Units
- Problems based on Perimeter
- Problems based on Area
Practical Geometry
- Construction of a Line Parallel to a Given Line, Through a Point Not on the Line
- Construction of Triangles
- Constructing a Triangle When the Length of Its Three Sides Are Known (SSS Criterion)
- Constructing a Triangle When the Lengths of Two Sides and the Measure of the Angle Between Them Are Known. (SAS Criterion)
- Constructing a Triangle When the Measures of Two of Its Angles and the Length of the Side Included Between Them is Given. (ASA Criterion)
- Constructing a Right-angled Triangle When the Length of One Leg and Its Hypotenuse Are Given (RHS Criterion)
Algebraic Expressions
Exponents and Powers
- Concept of Exponents
- Multiplying Powers with the Same Base
- Dividing Powers with the Same Base
- Taking Power of a Power
- Multiplying Powers with Different Base and Same Exponents
- Dividing Powers with Different Base and Same Exponents
- Numbers with Exponent Zero, One, Negative Exponents
- Miscellaneous Examples Using the Laws of Exponents
- Decimal Number System Using Exponents and Powers
- Crores
Symmetry
Visualizing Solid Shapes
- Perimeter Formulas
- Example 1
- Example 2
- Example 3
- Example 4
- Activity: Race Track Problem
- Key Points and Common Mistakes to Avoid
Perimeter Formulas
| Shape | Formula |
|---|---|
| Rectangle | P = 2 × (l + b) |
| Square | P = 4 × side |
| Equilateral Triangle | P = 3 × side |
| Regular Pentagon | P = 5 × side |
| Regular Hexagon | P = 6 × side |
Example 1
Problem: A rectangular field has length = 200 m and breadth = 160 m. Find:
- the perimeter of the field.
- the length of the fence of this field.
- the cost of fencing the field at the rate of ₹50 per meter.
Solution:
(i) The perimeter of the field = 2 × (length + breadth)
= 2 × (200 m + 160 m)
= 2 × 360 m = 720 m
(ii) The length of fence = The perimeter of the rectangular field
= 720 m
(iii) The cost of fence = Length of fence × Rate of fence
= 720 m × ₹50 per metre
= ₹ 36000
Example 2
Problem: Each side of a square field is 60 m. Find the cost of fencing this square field at the rate of ₹150 per meter.
Solution:
Perimeter of the square field = 4 × side
= 4 × 60 m = 240 m
Length of required fence = 240 m
The cost of fence = its length × its rate
= 240 m × ₹150 per metre
= ₹ 36000
Example 3
Problem: Find the perimeter of:
- an equilateral triangle of side 13 cm.
- an isosceles triangle with each equal side = 10 cm and the third side = 15 cm.
- a regular pentagon with side = 12 cm.
- a regular hexagon with side = 9 cm.
Solution:
The perimeter of equilateral triangle = 3 × side
= 3 × 13 cm = 39 cm
Perimeter of an issosceles triangle = 10 cm + 10 cm + 15 cm
= 35 cm
Perimeter of given pentagon = 5 × side
= 5 × 12 cm = 60 cm
Perimeter of given hexagon = 6 × 9 cm
= 54 cm
Example 4
Problem:
-
Akshi runs on the outer rectangular track
-
Toshi runs on the inner rectangular track
-
Akshi completes 5 rounds
-
Toshi completes 7 rounds
We are asked: Who ran a longer distance?
Solution:
From the diagram and description:
-
Outer track (Akshi’s):
Length = 70 m
Breadth = 40 m -
Inner track (Toshi’s):
Length = 60 m
Breadth = 30 m
Distance covered by Akshi:
Akshi's one round: P = 2 × (l + b) = 2 × (70 + 40) = 2 × 110 = 220
Number of rounds : 5
Total distance: 5 × 220 = 1100 m
Distance covered by Toshi:
Toshi's one round: P = 2 × (l + b) = 2 × (60 + 30) = 2 × 90 = 180 m
Number of rounds: 7
Total distance: 180 × 7 = 1260 m
Toshi ran the longer distance.
Activity: Race Track Problem
To find where two runners should start on two different square tracks (inner and outer) so that both finish at the same place after running exactly 350 meters
Find perimeter:
-
Inner = 4 × 100 = 400 m
-
Outer = 4 × 150 = 600 m
Find the distance remaining from the finish line:
-
Inner runner:
400 - 350 = 50 m → Start 50 m behind the finishing line (Point A)
Mark point A at 50 m before the finish -
Outer runner:
600 - 350 = 250 m → Start 250 m behind the finishing line (Point B)
So, mark point B at 250 m before the finish
Conclusion:
Start points are marked so both finish together after 350 m.
Point A for inner runner, Point B for outer runner.
Key Points and Common Mistakes to Avoid
-
Perimeter is the total distance around the outer boundary of a closed shape.
-
Always measured in linear units (cm, m, km, etc.).
-
Identify the shape and write the correct formula.
-
A common mistake is forgetting to multiply by 2 in the rectangle formula.
-
Another mistake is omitting one or more sides when adding up the perimeter.
