Class 6 · Chapter 1
Knowing Our Numbers
Comparing and reading large numbers; Indian and international place-value systems; estimation; Roman numerals; use of brackets.
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Detailed theory
The Indian place-value system groups digits as ones, tens, hundreds, thousands, ten-thousands, lakhs, crores. The International system groups them as thousands, millions, billions. Both systems represent the same number — only the grouping differs. E.g. is 3 crore 5 lakh 72 thousand 145 (Indian) or 30 million 572 thousand 145 (International).
Key concepts & formulas
01
Indian system uses lakhs and crores; International uses millions and billions.
02
To compare numbers, first compare the number of digits, then compare digit by digit from left.
03
Estimation gives a quick approximate answer, useful in mental maths.
04
Roman numerals use the letters and rules for repetition and subtraction.
05
km m; kg g; litre mL.