CBSE · Class 7 · Mathematics · Chapter 15

Finding the Unknown

Represent unknown quantities using variables and solve simple equations through logical arithmetic steps.

13 lessons 55 min
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Lessons in this chapter

  1. 1Unknown Weights and Balanced ScalesUse balanced branches to discover unknown weights before writing equations.
  2. 2From Matchstick Patterns to EquationsTurn growing patterns and balance puzzles into mathematical sentences.
  3. 3Trial, Error, and Preserving EqualityMove from sensible trials to operations that keep an equation balanced.
  4. 4Solving Equations One Step at a TimeIsolate an unknown through justified steps and confirm the result.
  5. 5Unknowns on Both SidesBring related terms together while keeping both sides equal.
  6. 6Equations Hidden in PatternsCount one shape in two ways and use its rule to find a position.
  7. 7Equations for Everyday SituationsChoose an unknown carefully and model costs, savings, and grouped operations.
  8. 8Number Tricks and Equation ChainsFollow and reverse operations to explain tricks and create equations.
  9. 9Mind the Mistake, Mend the MistakeFind the first invalid step and repair the reasoning behind an answer.
  10. 10A Pinch of HistoryConnect algebra’s changing notation with the same enduring idea of equality.
  11. 11Equations from Diagrams and MachinesRead pictures and operation routes carefully before building an equation.
  12. 12Connected Word Problems and ChallengesCombine relationships, pattern counts, and equation reasoning in richer problems.
  13. 13Chapter Summary and PracticeConnect the chapter’s ideas and use them confidently in mixed problems.
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