Question

Note :This is not a question !!

Tutorial 3: Math tricks(contd.)


Hope you like my tutorial series,Do provide you feedback .You can get the previous ones @http://openstudy.com/users/aravindg

Answer 1

This trick is much famous but still I would like to add it to the series

Multiplication of 11 with any number. (You can't use this rule for other numbers)
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Let me explain this rule by taking examples

1) 234163*11 = 2---2+3---3+4---4+1---1+6---6+3---3 = 2575793
Means insert the sum of 2 successive digits and put 2 terminal digits in its place

2) 45345181*11 = 4---4+5---5+3---3+4---4+5---5+1---1+8---8+1---1 = 498796991

Here an extra case arises

Consider the following examples for that

3) 473927*11 = 4+1--- (4+7-10) +1--- (7+3-10) +1--- (3+9-10) +1--- (9+2-10)--- (2+7) ---7 = 5213197

4) 584536*11 = 5+1---(5+8-10)+1---(8+4-10)---(4+5)---(5+3)---(3+6)---6 = 6429896

Answer 2

And an additional one for those who knew it already (i dont want to dissappoint anyone :) )

Multiplication of 5 with any number (You can't use this rule for other numbers)
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Let me explain this rule by taking examples

1. 49*5 = 490/2 = 245.
2. 453*5 = 4530/2 = 2265.


Understand the rule by 1 more example
5649*5 = 56490/2 = 28245.

Answer 3

>>my tutorials are published on a daily basis .hope you enjoy these tricks !

Answer 4

Might be worthwhile to point out why multiplying by 5 like that works:
Because 5 is half of 10.

Answer 5

And the multiplication by 11 might make more sense if you start small, like with a two-digit number.

ex.1. 63 × 11 = 6 _ 3. In the _ goes (6+3).
63 × 11 = 693.

Note that there is room in the _ only for a one digit number.

78 × 11 = 7 _ 8. In the _ goes (7+8), but there is only room for the 5, so carry the 1.
78 × 11 = 858.

Doing the reverse of this process can also let you tell if a number is divisible by 11.
;-)

Answer 6

@AravindG what reference are you using for this tutorials ?
i have learned these exact tricks years ago from a book.

Answer 7

There's an app for Mac computers called Mathemagics. It has tons of tricks like this.

Answer 8

O.o
any windows or linux counterpart ?

Answer 9

Not sure. I searched it, and it's available on the iPhone, too (which is a bit more ubiquitous).

http://www.bluelightninglabs.com/apps/mathemagics

Answer 10

same trick can be applied when multiplied by 111. just take three consecutive digits sum also.
example :
431 * 111 = 4 ---4+3-----4+3+1-----3+1-----1 = 47841
15344 *111 = 1---(1+5)+1---(1+5+3-10)+1----(5+3+4-10)+1 ---(3+4+4-10)---(4+4)----4 = 1703184
and same for 1111 , 11111 and so on.

Answer 11

@CiffSedge thanks for adding that to the tutuorial :)
@hartnn its from a Indian book entitled "Vedic mathematics"

Answer 12

i used 'Vedic Maths made Easy' by Dhaval Bhatia

Answer 13

i see ... then its not surprising that you have seen these tricks before !
most math tricks are got from vedic texts as they encouraged mental thinking than blind working even from ancient time !