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.
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
HinduArabic numerals are as follows:
Roman Symbols

I

V

X

L

C

D

M

HinduArabic Symbols

1

5

10

50

100

500

1000

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