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# Knowing our Numbers

1. Numbers are  represented by ten symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 are called digits.
2. Numeral - A group of digits, denoting a number. For e.g. 237, 28
3. Notation - Representing a number by figures or digits.
4. Numeration - Expressing a number in words. For e.g. Two, three
5. Face Value - The digit itself is the face value of digit.
6. Place Value - The place value of a digit in a number depends on the place it occupies in the place value chart.

Figure:

Indian Place Value Chart

 Ten Crore Crore Ten lakh Lakhs Ten Thousands Thousands Hundreds Tens Ones 2 3 9 7 8 6 7 5 8 0 7 9 2 4
1. 2, 39, 786 $\longrightarrow$ Two lakh thirthy nine thousand seven hundred and eightly six.
2. 7, 58, 07, 924 $\longrightarrow$ Seven crore fifty lakh seven thousand nine hundred and twenty four.

International Place Value Chart

 Billion Hundred Million Ten Million Million Hundred Thousand Ten Thousand Thousand Hundred Tens Ones 2 3 9 7 8 6 7 5 8 0 7 9 2 4
1. 239, 786 $\longrightarrow$ Two hundred thirty nine thousand seven hundred and eighty six.
2. 75, 807, 924 $\longrightarrow$ Seventy five hundred million eight hundred seven thousand nine hundred and twenty four.

Decending Order $\longrightarrow$ Arranging numbers from bigger to smaller.

Ascending Order $\longrightarrow$ Arranging numbers from smaller to bigger.

Estimation

Rounding Off Numbers

Nearest Ten

1. Check the digit at ones place.
2. If the number at ones place is less than 5, then replace the ones digit by 0 and do not change the number.
3. If the digit at the ones place is 5 or more, then increase the tens digit by 1 and change the ones digit by 0.

Nearest Hundred

1. Check the digit at tens place.
2. If the number at tens place is less than 5, then replace the tens digit by 0 and do not change the number.
3. If the digit at the tens place is 5 or more, then increase the hundreds digit by 1 and change the ones digit by 1.