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NCERT Solutions for Ganita Prakash (Part 2) Chapter 5 Tales by Dots and Lines

Updated on 2026-09-05

About this chapter

The mean is the balance point of the data: the distances of the values below it add up to exactly the same total as the distances of the values above it. That is why there is only one mean. Adding a value bigger than the mean pulls the mean up; a smaller one pulls it down; a value equal to the mean changes nothing. Two values can be added on opposite sides so that the mean does not move at all. If every value goes up by k, the mean goes up by k. If every value is multiplied by k, the mean is multiplied by k. Both facts are proved with algebra in the chapter. The median is the middle value of the sorted data. Because it only counts positions, one stray extreme value barely moves it, while the same value can swing the mean a lot. With a frequency table, the mean is (sum of value × frequency)

  • The Balancing Act
  • –106Unchanging Mean!
  • –107Relatively Unchanged!
  • Relatively Unchanged!
  • Tinkering with Median
  • Finding the Unknown
  • Mean and Median with Frequencies
  • –113Spreadsheets
  • –116Section 5.1 The Balancing Act
  • –119Section 5.2 Visualising and Interpreting Data
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Exercises

  1. In-text Questions — The Balancing Act Page 103
  2. In-text Questions — The Balancing Act Page 104
  3. In-text Questions — The Balancing Act Page 105
  4. –106Unchanging Mean! — In-text Questions Page 105
  5. –107Relatively Unchanged! — In-text Questions Page 106
  6. Relatively Unchanged! — In-text Questions Page 107
  7. Tinkering with Median — In-text Questions Page 108
  8. Finding the Unknown — In-text Questions Page 109
  9. Mean and Median with Frequencies — In-text Questions Page 110
  10. –113Spreadsheets — In-text Questions Page 112
  11. –116Section 5.1 The Balancing Act — Figure it Out Page 113
  12. –119Section 5.2 Visualising and Interpreting Data — In-text Questions Page 116
  13. –120Space Jam: A Traffic Problem in the Future? — In-text Questions Page 119
  14. –121Catch the (Pattern in) Rain — In-text Questions Page 120
  15. –123Section 5.2 Visualising and Interpreting Data — Figure it Out Page 122
  16. –124Infographics — In-text Questions Page 123
  17. What can a Strip Say? — In-text Questions Page 125
  18. What can a Strip Say? — In-text Questions Page 126
  19. –127Data Story: Sleepy-Deepy — In-text Questions Page 126
  20. –132Section 5.2 Visualising and Interpreting Data — Figure it Out Page 127
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