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YOUR STUDY SPACE · CBSE

A Story of Numbers — Class 8 Mathematics

Ganita Prakash Part 1 · Chapter 3

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Chapter summary

This is a historical-mathematical chapter tracing how humans learned to count and to write numbers. Counting begins with one-to-one mapping — matching each object to a stick, a sound, or a symbol — leading to the idea of a number system as a standard ordered sequence. Early systems counted in groups (the Gumulgal of Australia counted in twos) and then used landmark numbers, as in the Roman system with . A major breakthrough was the idea of a base: choosing landmark numbers that are powers of a fixed number gives a base- system, of which the Egyptian system (base ) is an example. The next leap was place value, where a symbol’s position fixes which power of the base it represents — seen in the Mesopotamian (base ), Mayan and Chinese systems. The crowning idea was the Hindu number system: a base- place-value system with ten digits including , treated as a number in its own right by Aryabhata and codified by Brahmagupta. Because of , every number can be written unambiguously with finitely many symbols.
Counting and one-to-one mappingEarly number systemsRoman and landmark numbersThe idea of a basePlace value and the role of zero

Key ideas & terms

Number system
A standard ordered sequence of objects, names, or symbols used to count and represent quantities.
Numeral
A written symbol that represents a number within a number system, such as or .
Landmark number
A reference number given its own symbol, used to group and build other numbers (e.g. in Roman).
Base-\(n\) system
A system whose landmark numbers are the powers of a fixed number :
Place value system
A system in which a symbol’s position determines which landmark (power of the base) it stands for.
Role of zero
A placeholder and a number in its own right that lets all numbers be written unambiguously with finitely many digits.

Extra questions & answers

What is one-to-one mapping in counting?

Pairing each object to be counted with exactly one element of a standard sequence, with no element reused.

What are the landmark numbers of a base- system?

The powers of :

Which base does the Egyptian number system use?

Base ; each landmark number is ten times the previous one.

Why is the Mesopotamian system called sexagesimal?

Because it is a base- system, with landmark numbers

What single idea distinguishes a place-value system?

The position of a symbol, not just the symbol itself, determines its value.

Why was zero a revolutionary idea?

It acts as a placeholder for empty positions and is itself a number, removing ambiguity from written numerals.

Which civilisation gave the world the modern -digit system?

It originated in India (the Hindu number system) about years ago.

Write using Roman landmark grouping.

, grouping .

Why could the Roman system not write arbitrarily large numbers easily?

It needed new symbols for each new large landmark, since it lacks a base and place value.

Who codified the arithmetic of zero, and when?

Brahmagupta, in his work Brahmasphutasiddhanta in CE.