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NCERT Solutions for Class 8th Maths Chapter 5 Tales by Dots and Lines

Updated on 2026-09-08

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