3. DECIMAL FRACTIONS

IMPORTANT FACTS AND FORMULAE

I. Decimal Fractions : Fractions in which denominators are powers of 10 are known as decimal

fractions.

Thus ,1/10=1 tenth=.1;1/100=1 hundredth =.01;

99/100=99 hundreths=.99;7/1000=7 thousandths=.007,etc

2. H.C.F. AND L.C.M. OF NUMBERS

IMPORTANT FACTS AND FORMULA


I. Factors and Multiples :
If a number a divides another number b exactly, we say that a is a factor of b. In this case, b is called a multiple of a.


II. Highest Common Factor (H.C.F.) or Greatest Common Measure (G.C.M.) or
Greatest Common Divisor (G.C.D.):
The H.C.F. of two or more than two numbers is
the greatest number that divides each of them exactly.
There are two methods of finding the H.C.F. of a given set of numbers :


1. Factorization Method : Express each one of the given numbers as the product
of prime factors.The product of least powers of common prime factors gives H.C.F.

1. NUMBERS

IMPORTANT FACTS AND FORMULA

I..Numeral : In Hindu Arabic system, we use ten symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

called digits to represent any number.

A group of digits, denoting a number is called a numeral.

We represent a number, say 689745132 as shown below :

Ten Crores (108)	Crores (107)	Ten Lacs (Millions) (106)	Lacs (105)	TenThousands (104)	Thousands (103)	Hundreds (102)	Tens( 101)	Units (100)
6	8	9	7	4	5	1	3	2

We read it as : 'Sixty-eight crores, ninety-seven lacs, forty-five thousand, one hundred and thirty-two'.