Making Your Math Simple Part II - Multiplication With 11 in Just 5 Seconds
Author: Rajinder Goswami
Improving Your Calculating Speed.
Multiplying with 11
Multiplying by 11 is very easy and very interesting also.
For Example take 12345 x 11
Just forget about 11 and concentrate on 12345
Step 1 Take last digit of 12345 (i.e. 5) to the answer: Ans 5
Step 2 Add last digit of 12345 with immediate neighbor
i.e. 5+4=9
take it to answer Ans 95
Step 3 Add Next two neighbors of 12345
i.e 3+4=7
take it to answer
Ans 795
Step 4 Add Next two neighbors of 12345
i.e 2+3=5
take it to answer Ans 5795
Step 5 Add Next two neighbors of 12345
i.e 1+2=3
take it to answer
Ans 35795
Step 6 Take first digit of 12345 to answer :
Ans 135795
So Answer is 135795
Example:
120342 x 11
Lat digit taken to the answer 120342 Ans 2 Last digit added to neighbor 120342 Ans 62 Next two neighbors added 120342 Ans 762 Next two neighbors added 120342 Ans 3762 Next two neighbors added 120342 Ans 23762 Next two neighbors added 120342 Ans 323762 First digit taken to the answer 120342 Ans 1323762
So the Answer is 1323762
In case of carry, the carry is added to the total of neighbors
Example:
226987 x 11 Lat digit taken to the answer 226987 Ans 7 Last digit added to the neighbor 226987 Ans 57 ‘1’ carried over Next two neighbors added + carry 226987 Ans 857 ‘1’ carried over Next two neighbors added + carry 226987 Ans 6857 ‘1’ carried over Next two neighbors added + carry 226987 Ans 96857 Next two neighbors added 226987 Ans 496857 First digit taken to answer 226987 Ans 2496857
Example :-
792421 x 11
Lat digit taken to the answer 792421 Ans 1 Last digit added to the neighbor 792421 Ans 31 Next two neighbors added 792421 Ans 631 Next two neighbors added 792421 Ans 6631 Next two neighbors added 792421 Ans 16631 ‘1’ is carried over Next two neighbors added + carry 792421 Ans 716631 ‘1’ is carried over First digit + carry taken to answer 792421 Ans 8716631
The problem can be solved in JUST one line
4526841 x 11
49795251
Try to apply the logic discussed in the previous examples and you will see that problem is solved in a single line.
For more such tricks and tactics to make your math simpler, please logon to http://www.magicwithmath.com
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Making Your Math Simple Part II - Multiplication With 11 in Just 5 Seconds
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