9. 7) DECIMAL NUMBERS
"Decimal number" is often used
to mean a number that uses a
decimal point followed by digits
that show a value smaller than one.
Example: 45.6 (forty-five point six)
is a decimal number.
12. FACTS ABOUT FACTORS
1) Factors of a number are written in ascending order.
2) The lowest factor of every number is 1.
3) The highest factor of every number is the number itself.
4) The factors of any numbers are finite.
5) The factor of a number is its complete divisor i.e.
remainder is 0. For example, as we know 6 is the factor of
12 the answer is 2 and there is no remainder.
14. FACTS ABOUT MULTIPLES
1) If you need to know the multiples of any number you need
to remember the table of that number.
2) The lowest multiple of any number is the number itself.
3) The highest multiple of any number is infinity.
4) The multiples of 2 are even numbers.
20. DIVISIBILITY RULE : -
There are some rules which
help us to find that a
number (no matter how
big) is divisible by the given
divisor without doing any
calculation.
21. DIVISIBILITY RULE OF 1
Each and every number is
divisible by 1 because 1 is the
factor of every
number.
22. DIVISIBILITY RULE OF 2
A whole number whose last
digit is Even is divisible by 2.
45 678
4 539 246
3 957
23. DIVISIBILITY RULE OF 3
Add the digits of the number,
if the sum is multiple of 3
then the whole number is
divisible by 3.
44 = 4 + 4 = 8
45 = 4 + 5 = 9
24. DIVISIBILITY RULE OF 4
If the last two digits of a
number are 00 or form a
number which is divided by 4
then the whole
number is divisible by 4.
48 247
48 200
25. DIVISIBILITY RULE OF 5
If the last digit is 0 or 5,then
the whole number is divisible
by 5.
200
23 465
389 671
26. DIVISIBILITY RULE OF 6
If the number is divisible by 2
and 3 both then it means that
it is divisible by 6 as well.
23 908
6 342
27. DIVISIBILITY RULE OF 7
Double the ones place i.e.
multiply by 2 . Subtract it from
the rest of the number . If the
answer is multiple of 7 , then
the whole number is divisible
by 7.
693
28. DIVISIBILITY RULE OF 8
If the last three digits of a
number are 000 or form a
number which is divided by 8
then the whole number is
divisible by 8.
3 294 732
3 294 000
29. DIVISIBILITY RULE OF 9
Add the digits of the number, if
the sum is multiple of 9 then the
whole number is divisible by 9.
65 241 = 6+5+2+4+1 =18
9 854 = 9+8+5+4 = 26
30. DIVISIBILITY RULE OF 10
The last digit of the number
should be 0.
257 890
25 789
33. 1) TREE METHOD
Suppose, we have to find the prime factors of
16.
1. We consider the number 16 as the root of the
tree.
2. We write a pair of factors as the branches of
the tree i.e., 2 × 8 = 16
3. We further factorize the composite factor 8 as
4 and 2, and again the composite factors 4 as 2
and 2.
We repeat the process again till we get the prime
factors .
34. 2) DIVISION METHOD
I: First we divide the number by the smallest
prime number which divides the number exactly.
II: We divide the quotient again by the smallest
or the next smallest prime number if it is not
exactly divisible by the smallest prime number.
We repeat the process again and again till the
quotient becomes 1. Remember, we use only
prime numbers to divide.
III: We multiply all the prime factors.
Remember, the product is the number itself.