Schooling · Class 7 · Mathematics · Expressions using Letter-Numbers · Chapter on a page
CBSE Class 7 · Mathematics · NCERT Ganita Prakash
Expressions using Letter-Numbers: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 26 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
This note's current text has no applied fact-check on record.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- A variable is a letter (like x, y, n…
- An algebraic expression is a…
- A term is a single part of an…
- The coefficient is the number…
- A constant is a term without any…
- Like terms have the same variable…
- We can only add or subtract like…
- Formulas and facts
- Expression = terms joined by + or −…
- Term = coefficient × variable, or…
- Like terms = terms with exactly the…
- To add like terms
- To subtract like terms
- Unlike terms cannot be combined.…
- A variable alone (like x) has…
- Watch out for
- Treating unlike terms as like terms
- Forgetting that a variable alone has…
- Ignoring the sign before a term
- Adding coefficients of unlike terms
- Confusing expressions with equations
What this chapter is about
In mathematics, we often use letters to stand for numbers. These letters are called variables because their value can vary or change. When we combine variables with numbers using operations like addition, subtraction, multiplication and division, we create algebraic expressions.
Key ideas
- A variable is a letter (like x, y, n or p) that represents an unknown or changing number.
- An algebraic expression is a combination of variables, numbers and operations. For example, 3x + 5 is an expression.
- A term is a single part of an expression separated by + or − signs. In 4a + 7b − 2, the terms are 4a, 7b and −2.
- The coefficient is the number multiplied with a variable. In 6m, the coefficient is 6.
- A constant is a term without any variable. In 5n + 9, the constant is 9.
- Like terms have the same variable raised to the same power. 3x and 7x are like terms. 3x and 3y are not like terms.
- We can only add or subtract like terms. Unlike terms stay separate.
- Expressions help us describe patterns and real-life situations in a short, general way.
Formulas and facts to remember
- Expression = terms joined by + or − signs.
- Term = coefficient × variable, or just a constant.
- Like terms = terms with exactly the same variable part. Example: 2p and 5p are like terms.
- To add like terms: add their coefficients. Example: 4x + 3x = 7x.
- To subtract like terms: subtract their coefficients. Example: 9y − 4y = 5y.
- Unlike terms cannot be combined. Example: 3a + 2b stays as 3a + 2b.
- A variable alone (like x) has coefficient 1. So x means 1 × x.
Common mistakes
- Treating unlike terms as like terms → Only combine terms that have the same variable. 3x + 2y cannot become 5xy.
- Forgetting that a variable alone has coefficient 1 → Remember that y means 1y, so y + 5y = 6y.
- Ignoring the sign before a term → The sign belongs to the term. In 8 − 3p, the term is −3p, not 3p.
- Adding coefficients of unlike terms → 4a + 5b is already simplified. Do not write 9ab.
- Confusing expressions with equations → An expression has no equal sign. 2x + 3 is an expression, but 2x + 3 = 11 is an equation.
Quick revision
- A variable is a letter that stands for a number.
- Terms are separated by + or − signs.
- Coefficient is the number in front of a variable.
- Like terms have the same variable; only these can be combined.
- To combine like terms, add or subtract their coefficients.
- Constants are terms with no variable.