Class 6 Chapter 1: Knowing our Numbers

# Class 6 Chapter 1: Knowing our Numbers

Important Concepts and Formulas

1.      The ten symbols such as 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 are called digits.

2.      A single digit or a group of digits form a number.

3.      The process of writing a number using the digits is called notation, and writing a number in words is called numeration.

4.      There are two systems of numerations: Indian and International system of numeration.

5.      In the Indian system of numeration, first comma is placed after 3 digits starting from right. These three places form ones period. Other periods are Thousands, Lakhs and Crores.

6.      In the Indian system, all periods (except ones) have two places each.

7.       In the international system, each period has 3 places.

8.      The face value of a digit in a number is the digit itself.

9.      The place value of a digit in a number depends on the position (place) of the digit in the number.

10. Estimation gives us a rough idea of the answer to be obtained after operations on the numbers.

11. To round off a number to the given rounding digit (10, 100, 1000, ...), we should check only the number to the right of the rounding digit.

12. There are 7 symbols which are used to write various numbers in Roman numerals. Their values corresponding to Hindu-Arabic numerals are as follows:

 Roman Symbols I V X L C D M Hindu-Arabic Symbols 1 5 10 50 100 500 1000