MATHS TRICKS FOR MULTIPLICATIONHelpful for Teachers and Students
Multiplication of any two numbers, lies between 11 and 19
I explain this rule by taking example :
14 X 19 = (14 + 9) X 10 + (4 X 9) = 230 + 36 = 266
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.
For Example.
13 X 18 = (13 + 8) X 10 + (3 X 8) = 210 + 24 = 234
12 X 19 = (12 + 9) X 10 + (2 X 9) = 210 + 18 = 228
Multiplication of 11 with any number of 3 digits.
I explain this rule by taking example :
341 X 11 = 3---(3+4)---(4+1)---1 = 3751
Means insert the sum of first and second digits, then sum of second and third digits between the two terminal digits of the number
For Example :
254 X 11 = 2---(2+5)---(5+4)---4 = 2794
Here is an extra case arises
349 X 11 = 3--- (3+4) +1--- (4+9-10) ---9 = 3839
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.
For Example :
429 X 11 = 4--- (4+2)+1--- (2+9-10) ---9 = 4719
798 X 11 = 7+1---(7+9-10)+1---(9+8-10)---8 = 8778
Means, if both sum of two digits of the number is greater than 10, add 1 to first disit, then add 1 to sum of first two disit and subtract 10 to the associated digit, then subtract 10 to the sum of last two disit.
For Example :
697 X 11 = 6+1---(6+9-10)+1---(9+7-10)---7 = 7667
