Class 9 · Chapter 10
How Quantities Combine: Understanding Data
Organising raw data, frequency distributions, and the three big averages: mean, median, mode.
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Ganita Manjari · Class 9 (2026-27)
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Tip: NCERT updated the syllabus for 2026-27. The links above open the latest edition on the official portal — chapter titles and numbering may differ from the notes shown here.
Detailed theory
A list of 30 exam scores tells you little. A frequency table (0-10, 10-20, …) suddenly reveals whether the class is bunched up or spread out. That is the whole point of data handling: turn noise into a story.
Key concepts & formulas
01
Raw data frequency distribution: group observations and count.
02
Class-width , class-mark .
03
Mean of values: ; for a frequency table: .
04
Median: middle value after sorting; if even, average of the two middles.
05
Mode: value that occurs most often.
06
Range max min captures the spread at a glance.