MULTIPLICATION OF ANY TWO NUMBERS, LIES BETWEEN 11 AND 19

 Let me explain this rule by taking examples
13*19 = (13+9)*10 + (3*9) = 220 + 27 = 247
Means add first number and last digit of the second number take zero in the third place of this number then add product of last digit of the two numbers in it. 

Example

18*14=(18+4)*10+3*9=220+27=247

Exclusive Division Rule for 7

Let me explain this rule by taking examples

If you had 343, you would double the last digit to get six, and subtract that from 34 to get 28.
If you get an answer divisible by 7 (including zero), then the original number is divisible by
seven. If you don't know the new number's divisibility, you can apply the rule again

EXAMPLE.

Example -:
623: 62 - (3 × 2) = 56 = 7 × 8
483: 48 − (3 × 2) = 42 = 7 × 6