Revision Notes for Class 7 Maths Chapter 4: Expressions Using Letter-Numbers

Quick revision notes summarizing all key concepts from Class 7 Maths Chapter 4 “Expressions Using Letter-Numbers”. These Class 7 Mathematics Chapter 4 notes are ideal for quick revision just before exams.

Last Updated: September 23, 2026

• A letter-number (variable) is a letter used to represent an unknown or changing quantity in place of a specific number.
• An algebraic expression combines letter-numbers, numbers, and operations (+, −, ×, ÷), e.g. 3x + 5.
• A term is a part of an expression separated by + or − signs. In 3a + 5b − 7, the terms are 3a, 5b, and −7.
• Like terms have the same letter-number(s) raised to the same power (e.g. 4x and 7x are like terms; 4x and 4x² are not).
• To simplify an expression, combine like terms by adding/subtracting their numerical coefficients.
• When removing brackets preceded by a minus sign, the sign of every term inside the bracket flips.
• Perimeter formulas: triangle = 3a, square = 4a, pentagon = 5a, hexagon = 6a, octagon = 8a (a = side length).
• To add two expressions, combine like terms from both. To subtract, flip the sign of every term in the expression being subtracted, then combine like terms.
• Algebraic expressions can describe real-world patterns: costs (rate × quantity + fixed charge), matchstick/shape patterns (constant + step×increment), and number sequences (nth term formulas like 4n+1, 3n−2, etc.).
• To find the value of an expression for given letter-number values, substitute the values and simplify using the order of operations (BODMAS).

NCERT Solutions: Class 7 Maths Chapter 4
Extra Questions: Class 7 Maths Chapter 4

For the full chapter, see the Class 7 Maths book page and the Class 7 Maths Formulas Handbook.

Frequently Asked Questions

What is a variable, and why are letters used to represent it in mathematics?
A variable is a letter or symbol used to represent an unknown or changeable quantity, and letters allow general mathematical relationships to be written once and applied to many situations without separate equations for each number.

What is the difference between a constant and a variable in an algebraic expression?
A constant is a fixed value that does not change, such as the number 5, while a variable is a symbol like x or y that can represent different values depending on the situation being described.

Written by Satish

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