CBSE · Class 8 · Mathematics · Chapter 7

Proportional Reasoning-1

Compare quantities using ratios, rates and proportional relationships drawn from everyday situations.

8 lessons 55 min
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Lessons in this chapter

  1. 1Observing Similarity in ChangeDiscover proportional change by comparing resized images and distinguishing a common scale factor from equal additions or subtractions.
  2. 2Ratios and Their Simplest FormWrite ordered ratios, form equivalent ratios, simplify using the HCF and recognise proportion through equal simplest forms.
  3. 3Problem Solving with Proportional ReasoningUse equivalent ratios and scale factors in recipes, fair comparisons, changing ages, missing-term problems and visual investigations.
  4. 4Trairasika — The Rule of ThreeDerive cross multiplication from a shared scale factor, apply the Rule of Three with consistent units, and test whether direct proportion is appropriate.
  5. 5Sharing, but Not Equally!Divide a known whole into parts in a specified ratio, derive the general sharing formula and track how adding one component changes a mixture.
  6. 6Unit ConversionsConvert length, area and volume with the supplied factors, distinguish exact and rounded conversions, and use Celsius–Fahrenheit formulas with their offset.
  7. 7Applying Proportional ReasoningSolve all twelve final problem types by combining ratio simplification, fair comparisons, sharing, unit conversion and interpretation of practical answers.
  8. 8Chapter Summary and PracticeRevisit all seven lessons in learning order, compare methods, solve mixed revision problems and complete the source Binairo enrichment puzzles.
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