CBSE · Class 9 · Mathematics · Chapter 6

Measuring Space: Perimeter and Area

Develop methods for calculating perimeter and area while understanding how measurement formulas arise from geometric reasoning.

10 lessons 65 min
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Lessons in this chapter

  1. 1Perimeter of a ShapePerimeter is what happens when a shape asks you to walk all the way around it.
  2. 2Perimeter of a Circle and the Number πMeasure a circle’s boundary and π appears, as usual, without ever finishing.
  3. 3Length of an Arc and Perimeter PuzzlesEven a slice of a circle has a boundary bill to pay.
  4. 4Area of Rectangles and ParallelogramsRectangles and parallelograms may lean differently, but their areas know the truth.
  5. 5Area of a TriangleA triangle takes half the rectangle and still gets its own famous formula.
  6. 6Heron's Formula and Brahmagupta's FormulaWhen the height goes missing, Heron and Brahmagupta arrive with backup.
  7. 7Squaring a RectangleTurning a rectangle into a square sounds like magic, but area keeps the receipts.
  8. 8Area of a CircleThe formula πr² is short, but its consequences are very round.
  9. 9Area of Sectors and SegmentsSectors take the slice while segments keep the curved leftovers.
  10. 10Chapter Summary and PracticeAdd up the boundaries, areas, arcs and slices—then measure how much you remember.
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