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 + (8*4) = 220 + 32 = 252Multiplication of 11 with any number of 3 digits.
Let me explain this rule by taking examples
1. 352*11 = 3---(3+5)---(5+2)---2 = 3872
Means insert the sum of first and second digits, then sum of second and
third digits between the two terminal digits of the number
2. 213*11 = 2---(2+1)---(1+3)---3 = 2343
Example.
Here an extra case arisesConsider the following examples for that
1) 329*11 = 3--- (3+2) +1--- (2+9-10) ---9 = 3619
Means, if sum of two digits of the number is greater than 10, then add 1 to previous digit and subtract 10 to the associated digit.
2) 758*11 = 7+1---(7+5-10)+1---(5+8-10)---8 = 8338
Magical Division Rule For 2
If a number is divisible by two it will end in an even number or a 0.
Example.
For example28964
given number end with 2 then it will be divisible by 2.
and
89450
given number end with 0 it will also be divisible by 2.
Golden Division Rule For 3
If a number is divisible by three the sum of its digits will be divisible by 3.
Example.
372 = 3 + 7 + 2 = 12A corollary of this is that any number made by rearranging the digits of a number divisible by 3 will also be divisible by 3.
Exceptional Division Rule For 4
If a number is divisible by four the last two digit are divisible by 4 (or are zeros).
Example.
45624last two digit is 24
24 is divisible by 4 then 45624 is divisible by 4.
Incredible Division Rule For 5
If a number is divisible by five the last digit will be 5 or 0.
Example.
48905last digit is 5 then 48905 is divisible by 5
and
56890
last digit is 0 then 56890 is also divisible by 5
Exclusive division Rule for 8
If a number is divisible by eight the last three digits are divisible by 8
Read more at http://www.m4maths.com/maths-trick.php#Q5IBZhOk1KJAeZmm.99
Example.
4857248
last three digits are 248
248/8 = 31
Then 4857248 is divisible by 8
