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.

• 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.

Written by Satish

NCERTBooks.org is an independent educational resource run by a small team focused on making official NCERT textbooks easy to find, read, and download for students, parents, and teachers across India. We are not affiliated with NCERT or the Ministry of Education -- we organise publicly available NCERT content by class and subject, verify links against official sources, and build tools (like our in-browser reader) that make studying more convenient. Every guide we publish is written and reviewed by our team based on the actual NCERT curriculum and syllabus.