Knowing our Numbers

While comparing two numbers, the number with more digits is the greater number. If the number of digits are same then the number with the greater leftmost digit is larger. If this digit is also same, then look at the next digit and so on.

Ascending order means the arrangement from the smallest to the greatest. Descending order means the arrangement from the greatest to the smallest.

New numbers can be made by shifting the digits of the given number. Place value is a positional system in which the position of a number is used to determine the value of the number. Place values are ones, tens, hundreds, thousands, etc.

There is a pattern wherein when 1 is added to the greatest n-digit number, the smallest (n + 1) digit number is obtained.

The smallest four digit number is 1000 (one thousand). It follows the largest three digit number 999. Similarly, the smallest five digit number is 10,000. It is ten thousand and follows the largest four digit number 9999. To read and write the large numbers, the concept of expansion of numbers is used.

Use of commas: In the Indian system of numeration we have commas after 3 digits starting from the right and thereafter every 2 digits. The commas after 3, 5 and 7 digits separate thousand, lakh and crore respectively.

In the International system of numeration commas are placed after every 3 digits starting from the right. The commas after 3 and 6 digits separate thousand and million respectively.

Large numbers are needed in many places in daily life. Kilo shows 1000 times larger, centi shows 100 times smaller and milli shows 1000 times smaller, thus, 1 kilometre = 1000 metres, 1 metre = 100 centimetres or 1000 millimetres etc.

Estimation involves approximating a quantity to an accuracy required. A given number can be estimated to its nearest tens, nearest hundreds and nearest thousands.

To estimate products round off each factor to its greatest place, then multiply the rounded off factors.

Brackets are used to avoid confusion in the problems where more than one number operation need to be carried out. Calculations in brackets are to be done first.

Hindu-Arabic system of numerals are used in general. Another system of writing numerals is the Roman system. It is an early system of writing numerals and is used in many places, e.g., in clocks, in school timetables, etc.

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