**Divisibility Rules Workbook-1**

When we multiply a number by 1, 2,3, 4, etc. The products are known as multiples of the numbers.

**Important points :**

1. A number is a multiple of itself.

2. Every number is multiple of 1.

3. Multiples of a numbers are either greater than or equal to the number.

4. There are infinite multiples of a number.

**Divisibility rules :**

A number will be divisible by 2 if the digit at the unit place is divisible by 2.

A number will be divisible by 3 if the sum of digits of the number is divisible by 3

A number will be divisible by 4 if the last two digits of the number together are divisible by 4.

A number will be divisible by 5 if digit at the unit place is either 0 or 5.

A number will be divisible by 6 if the digit at the unit place of the number is divisible by 2 & sum of all digits of the number is divisible by 3.

Divisibility test of 7: Make two set of three nos. starts from unit digit then add the alternate sets, and find out the mutual difference, if it is 0 or any multiple of 7 then the given no. is divisible by 7.

A number will be divisible by 8 if the last 3 digits, all together, is divisible by 8.

A number will be divisible by 9 if sum of all it’s digits is divisible by 9.

Read More...**Factorisation of Numbers Workbook-1**

Factors are the numbers that are multiplied to give a product.

If a number ‘a’ is divided by ‘b’ and remainder is zero than ‘b’ is said to be factor of ‘a’

**Co-Prime Numbers:**

Two numbers (not necessarily prime) are co-prime, if they have only 1 as common factor.

e.g., (1, 2), (1, 3), (3, 4), (3, 10), (3, 8), (5, 6), (7, 8) etc.

These numbers are also called as relatively prime numbers.

**Note:**

(a) Two distinct prime numbers are always co-prime but converse need not be true.

(b) Consecutive numbers are always co-prime numbers.

**Twin Prime Numbers:**

If the difference between two prime numbers is two, then the numbers are called as twin prime numbers. e.g., {3, 5}, {5, 7}, {11, 13}, {17, 19}, {29, 31}.

Read More...**Factorisation of Numbers Workbook-2**

**Important points :**

1. 1 is a factor of every number. It is the smallest factor of a number.

2. Every number is a factor of itself. The greatest factors of the number is the number itself.

3. All the factors of the numbers are either less than or equal to the numbers.

4. Every number has at least two factors except number 1.

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