Expressions using Letter-Numbers

About this chapter

Expressions using Letter-Numbers is the introduction-to-algebra chapter of Class 7 Ganita Prakash Part 1. It introduces five core ideas. First, the notion of letter-numbers: letters such as a, s, n, c, j stand for numbers we do not yet know, and an expression like a + 3 or 2 × n captures a general rule. Second, writing algebraic expressions for everyday situations — Shabnam's age, Parthiv's matchstick L-pattern, Ketaki's coconut-jaggery costs, perimeters of regular polygons. Third, evaluating an expression by substituting numbers for its letter-numbers, and the common mistakes to avoid (3d means 3 × d, not 36 when d = 6). Fourth, simplification using like terms, distributive property, and bracket-opening rules — 5c + 3c + 10c = 18c, but 18c + 11d stays as it is. Fifth, picking patterns and writing formulas — number machines, matchstick triangles, calendar grids, traffic signals. CTET Paper 2 Mathematics tests this chapter through writing an expression from words, evaluating an expression at a given value, and identifying like or unlike terms. The four tests — Practice 15, Quiz 15, Hard 15, Mastery 30 — cover these ideas at the right depth.