Download Finding the Unknown – NCERT Class 7 Maths Chapter 15 PDF from the new NCERT Class 7 Maths book Ganita Prakash (2026-27). Read the chapter online or download the free PDF. A statement of equality between two algebraic expressions is called an equation. The part left of the ‘=’ sign is the LHS, the part right of it is the RHS.
Finding the Unknown PDF – Chapter 15 of Ganita Prakash (Part II)
Read the chapter online or download the PDF.
| Chapter | Download | |
|---|---|---|
| Chapter 15 PDF | Finding the Unknown | View PDF |
| Full book | NCERT Class 7 Maths – Ganita Prakash | View Book |
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What Is in Finding the Unknown? (Class 7 Maths Chapter 15)
- A statement of equality between two algebraic expressions is called an equation. The part left of the ‘=’ sign is the LHS, the part right of it is the RHS.
- Solving an equation means finding the value of the letter-number that makes LHS = RHS. Checking a solution means putting the value back in and seeing that both sides agree.
- A balanced weighing scale stays balanced when you remove the same weight from both pans. In exactly the same way, an equation stays true when the same operation is done on both sides — add, subtract, multiply or divide.
- Removing a term from one side puts its additive inverse on the other side: 2y + 7 = 21 becomes 2y = 21 − 7.
- Removing a factor from one side divides the other side by that factor: 2y = 14 becomes y = 14 ÷ 2. Removing a divisor multiplies the other side by it: u ÷ 15 = 6 becomes u = 6 × 15.
- Trial and error also works, but it is slow. For 2n + 1 = 99 you would have to guess your way to n = 49; the systematic method gets there in two steps.
- Real problems become equations once you name the unknown. Costs, savings, sequences of matchsticks and tiles, ages, angles of a triangle — all of them turn into a single line of algebra.
- This subject was called bījagaṇita in ancient India (bīja = seed). Aryabhata, Brahmagupta and Bhāskarāchārya solved such equations; Brahmagupta’s rule for Ax + B = Cx + D is x = (D − B) ÷ (A − C).
Quick revision – Finding the Unknown
| Idea | What it says | Example from the chapter | Result |
|---|---|---|---|
| Equation | Two expressions joined by ‘=’ | 2n + 1 = 99 | LHS = 2n + 1, RHS = 99 |
| Solving | Find the value that makes LHS = RHS | 2n + 1 = 99 | N = 49 |
| Balance rule | Same operation on both sides keeps equality | 11y + (−5) = 61, add 5 to both sides | 11y = 66 |
| Removing a term | Its additive inverse appears on the other side | 2y + 7 = 21 | 2y = 21 − 7 = 14 |
| Removing a factor | Divide the other side by that factor | 2y = 14 | Y = 14 ÷ 2 = 7 |
| Removing a divisor | Multiply the other side by that divisor | U ÷ 15 = 6 | U = 6 × 15 = 90 |
| Unknowns on both sides | Move them to one side first | 6y + 7 = 4y + 21, subtract 4y | 2y + 7 = 21, so y = 7 |
| Trial and error | Substitute values till LHS = RHS | 5x − 4 = 7 | X = 11/5 — guessing is slow here |
| Framing an equation | Name the unknown, then write the fact | ₹25 a plate + ₹50 delivery = ₹500 | 25p + 50 = 500, p = 18 |
| No solution | Two sides can never be equal | X + 4 = x + 5 | No value of x works |
| Brahmagupta’s rule | For Ax + B = Cx + D | 650m + 4000 = 500m + 5050 | M = (5050 − 4000) ÷ (650 − 500) = 7 |
| Checking | Substitute the answer back | X = 11/5 in 5x − 4 | 11 − 4 = 7 = RHS ✓ |
Old NCERT vs New – Class 7 Maths
This chapter is from Ganita Prakash, the new NCERT Class 7 Maths book (NCF-SE 2023, used from 2025-26). It replaced the old book “Mathematics”, so chapter numbers and names differ from older PDFs.
Solutions and All Chapters
Answers to the exercises and the full chapter list of Ganita Prakash:
Finding the Unknown – Overview
| Class | Class 7 |
| Subject | Maths |
| Book | Ganita Prakash – new NCERT book |
| Part | Part II |
| Chapter | 15 of 15 – Finding the Unknown |
| Book pages | Part II, 164 – 190 |
| Edition | NCERT Reprint 2026-27 |
| Session | 2026-27 |
| Free – read online or download |
Class 7 Maths Chapter 15 – FAQs
Where can I download Finding the Unknown Class 7 PDF?
From the download table on this page – the chapter PDF is free, and the full book is linked too.
What is Class 7 Maths Chapter 15 about?
A statement of equality between two algebraic expressions is called an equation. The part left of the ‘=’ sign is the LHS, the part right of it is the RHS.
Is Finding the Unknown from the new NCERT Class 7 Maths book?
Yes. It is chapter 15 of ganita prakash (part ii), the new NCERT Class 7 Maths book for 2026-27.
Is this the latest NCERT edition for 2026-27?
Yes – the PDF is NCERT’s latest edition for the 2026-27 session.
Where are the NCERT Solutions for Class 7 Maths Chapter 15?
Open the NCERT Solutions link above for answers to the exercise questions.