Topics
Number System (Including Estimation and Approximation)
Number System
Theme 1 : Numbers
Number System(Consolidating the Sense of Numberness)
Ratio and Proportion
Theme 2 : Ratio, Proportion and Arithmetic Problems
Numbers in Indian and International Systems (With Comparison)
Estimation
Theme 3 : Algebra
Numbers in India and International System (With Comparison)
Algebra
Natural Numbers and Whole Numbers (Including Number Line and Patterns)
Place Value
Negative Numbers and Integers
Geometry
Theme 4 : Geometry
Mensuration
Theme 5 : Mensuration
Sets
Natural Numbers and Whole Numbers (Including Patterns)
Negative Numbers and Integers
Theme 6 : Statistics
Data Handling
Fractions
Number Line
Decimal Fractions
Playing with Numbers (Including H.C.F. and L.C.M.)
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
Ratio and Proportion (Including Unitary Method)
Sets
Percent (Percentage)
Idea of Speed, Distance and Time
Ratio
Fundamental Concepts (With operations on Algebraic Expressions)
Proportion (Including Word Problems)
Unitary Method
Framing Algebraic Expressions (Including Substitution and Linear Equations)
Fundamental Concepts (Including Angles and their Properties)
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
Triangles (Including Types and Properties of Triangles)
Quadrilaterals
Percent (Percentage)
Circles
Idea of Speed, Distance and Time
Symmetry
Fundamental Concepts
Constructions
Fundamental Operations (Related to Algebraic Expressions)
Substitution (Including Use of Brackets as Grouping Symbols)
Recognition of Solids
Framing Algebraic Expressions (Including Evaluation)
Perimeter and Area of Plane Figures
Data Handling (Including Mean and Median)
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
- Formula: Perimeter of an Equilateral Triangle
- Example 1
- Example 2
- Key Points Summary
Introduction
Have you ever wanted to put a boundary around something? Think about these real situations:
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Your school wants to put a fence around a triangular garden
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You need to buy a decorative border for a triangular picture frame
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A runner needs to know how far around a triangular running track
In each of these situations, we need the perimeter — the total length around the shape.
An equilateral triangle is a triangle in which:
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All three sides are equal in length.
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All three angles are equal (each is 60°).
Formula: Perimeter of an Equilateral Triangle
For an equilateral triangle with side length = s
P = s + s + s
= 3 × s
Perimeter = 3 × Length of one side
Example 1
Problem: An equilateral triangular frame has a perimeter of 27 cm. What is the length of each side?
Solution:
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Perimeter = 27 cm
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We know: P = 3s
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So: 27 = 3s
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Divide both sides by 3: s = 27 ÷ 3
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s = 9 cm
Answer: Each side is 9 cm long.
Example 2
Problem: A school wants to build a fence around a triangular garden. The triangular garden is equilateral with each side measuring 4 meters. How much fencing material is needed?
Solution:
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Each side of triangle = 4 meters
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It's an equilateral triangle, so all sides are equal
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Perimeter = 3 × 4 = 12 meters
Answer: The school needs 12 meters of fencing material.
Key Points Summary
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An equilateral triangle has 3 equal sides
- For equilateral triangles: Perimeter = 3 × side length
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Use the formula: P = 3s (where s = length of one side)
- Always include the unit of measurement (cm, m, mm, etc.)
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If the perimeter P is known, the side length s = P ÷ 3.
