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Simple tricksHow to multiply any two digits number by 11

Let’s say that you want to find the product of 36 and

11. One way to find it would be to multiply 36 by10 and then add 36 on the result. There is, however,

a simple tric that’ll do the !ob for any two di"its

number. To find out the result, write the first di"itfollowed by the addition of the first and second

di"it, followed by the second di"it.#$ample%

&hat happens if the sum of the two numbers is

 bi""er than '( )n this case you add 1 to the first

number, followed by the last di"it of the addition ofthe two numbers, and then a"ain you add the second

number 

Square any two digits number that ends with 5

*alculatin" the s+uare of a number below 100 ise$tremely simple. )f you want to find the s+uare of

- for e$ample, you simply have to tae the first

di"it /, multiply it for the ne$t hi"her number 3/,and then add - to the result.

Multiply any two digits numbers with the same

first digit and the second digit that sums up to 10

Let’s say that you want to multiply and

to"ether. 2otice that they both start with , and thatthe sum of their second di"it is 10. )n this case

there’s a simple rule that you can use to find their

 product. imply multiply the first di"it / for thene$t hi"her number -/ and then append the product

of their second di"its.

 2ote that if the product of the second di"its is below

ten, you have to add a 0 in front of it.

Multiply by 9

To multiply by ', simply multiply by 10 and then

subtract the number itself.Quickly find percentages

• To find out the 1-4 of a number, divide it

 by 10 and the add half of it.

• To find out the 04 of a number, divide it

 by 10 and multiply the result by two.

• To find out the -4 of a number, divide it by

10 and the divide it by two.

ddition&hen we were at school, we have been tau"ht how

to sum two or more numbers to"ether by usin" theri"ht to left approach. &ith this method, you first

sum the decimal part of the number, then you move

to the hundreds and so on. This wors "ood on paper, but it’s a pain when you’re doin" mental

calculations. 5ortunately, the solution is very easy.

!eft to right approach

)nstead of usin" a ri"ht to left approach, we canstart from the left and move to the ri"ht. Tae the

followin" e$ample%

sually, you would first sum up to -, and thenand 30 to the result. 7ut by usin" the left to ri"ht

approach, you first sum up 30 to -, and then you

add to the result. 8lthou"h this e$ample is verysimple, you’ll see the advanta"es of this method as

you start to use it.

)f you’re worin" with three di"its numbers, the process is the same.

This e$ample is a bit more complicated than the

 previous one, yet it’s very easy to solve usin" the

left to ri"ht approach. 9ou first start by addin" 600to -', which results in 10-'. 2ow the problem is

simplified to 10' : 3;. 9ou simplify it even further

 by addin" 30 to 10', and then you finally add ; tothe result.

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SubtractionLie with addition, you can use the left to ri"ht

approach for subtractin" to numbers to"ether. This

time, however, it may feel uncomfortable to eeptrac of borrowin"s a borrowin" occurs when you

subtract a number to a bi""er one, lie 16 < '/. Let’s

see an e$ample of this.

)n this case, you first start by subtractin" 10 to 6,

resultin" in -, and now you only have to subtract ;

to -. 9ou can, however, subtract 0 to 6 and add 3to the result. This way you don’t have to worry

about borrowin"s.

"sing complements to simplify subtractions e#en

more

There is a way to easily calculate 3 or di"its

subtractions very +uicly in your head. Thistechni+ue maes use of complements. 5or e$ample.

let’s say that you’re facin" the followin" problem%

)nstead of followin" the standard left to ri"ht

approach, you could solve this problem bysubtractin" 00 to 6; and then add bac to the

result. is the difference from 100 and -. 8 "ood

+uestion is% how do you find (

 2ote that there’s a simple pattern for calculatin" thesecond number. )n particular, the sum of the first

di"its always sum up to ', and the sum of the

second di"its always sum up to 10. The onlye$ception is when the number ends with 0, which is

simpler.

9ou can use this techni+ue to solve any subtractionvery easily.

Multiplication)n order to solve simple multiplications, it’s helps a

lot bein" comfortable with the multiplication table

for numbers below 10.8s you may have already "uessed, we’re "oin" to

use the left to ri"ht approach to solve simple

multiplication very easily. Tae the followin"e$ample%

&e can reduce it by first calculatin" 30 = ; which

is lie 3 = ; plus a 0/ and then add 6 = ; on theresult.

This approach can be used for even lar"er numbers.

 2ote that you can also round up instead of roundin"

down%

"ser contributionsthe followin" are some math trics contributed by

the users.

Multiply by 5Contributed by Scott.

To multiply - simply cut the > in half then multiply

 by 10.

e". 1;?-1@ of 1; A .-

.- ? 10 A -

Multiply numbers with multiple digitsContributed by Tom Peterson

se this tric when multiplyin" numbers withmultiple di"its

let BaCbCcCdDE represent di"its of a number ab $ cd A a$c/, a$d : b$c/, b$d/

the commas represent separation of di"its, so Fa$cG

represents the di"it in the hundreds place, etc.e"/ 3 = 1 A =1/, = : 3=1/, 3=/

: 3

A ,11,1in the event of double di"its in the same di"it place,

the number in the di"it’s place startin" with the

unit’s place/ carries the ten’s place di"it of the di"it place to the followin" di"it place Hwhat a mouthfulIJ

lie in this instance

A , 11, 1 A , 1, A 3, ,

the answer is 3the theory behind this is the Fdistribution propertyG

of numbers commonly used with e+uations lie $ :

1/$ : /A0 to mae $K : -$ : A0the same principles can be applied with 3 di"it

numbers as well

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abc $ def A a$d/,a$e:b$d/,a$f:b$e:c$d/,

b$f:c$e/,c$f/for multiplyin" di"it with 3 di"it numbers, !ust use

the 3=3 di"its method but use a ero in the hundreds

 place of the di"it number 

Square a number close to 10$%Contributed by Prerak 

Medic mathematics provides lots of short cuts lie

shown here.e.".N

)f you need to s+uare a number close to 10Kn, you

can do so easily. Lie if you want 'K, lets tae itsanswer as abcd .

 2ow, ' is before 100, so subtract from ', i.e.

you "et ab as . 5or findin" cd , s+uare i.e. 6.ence the s+uare of ' comes as 6.

5or s+uare of ;, let the answer is abcd  a"ain. ere

; is 13 short of 100, so subtract 13 from ; 9ou"et ; as ab. 5or findin" cd , s+uare 13 i.e. 16'.

ince cd  is only of two di"its, add this e$tra 1 to ab.o the answer becomes ;-6'.

Square two digits ending with 5Contributed by alwayslovely

To s+uare di"it numbers endin" with P-’ e" ;- =

;-1. The answer will end with P-’

. Tae the first di"it P;’ multiply by the number

after P;’ AQ ; = A -6;- = ;- A -6-

Test it out with '- = '-.

Rid you "et 1-(Squaring any numberContributed by joe

tae any number and find out how much to add to

"et it to the nearest tens subract and add thatnumber to the ori"nal number multiply add the

s+uare

e$ample%''':1/ '''N1/ : 1K/

''/ 1000/ : 1

'''K : ''001

Squaring a number*ontributed by Syan

8 math tric ) noticed when ) was youn". )f you are

s+uarin" a number it is always e+ual to the total of

the number times subtract one of the previous

s+uared number. This is helpful if you dont want towrite it out. 5or instance most people now that

10=10A100 or 11=11A11 even 1=1A1 so lets

say you dont now 13=13. )ts e+ual to 13=/N1plus the previous s+uared number which was

1=1/1A16'

Squaring two digit numbers

*ontributed by hy!uuppose 87 is the number,

Then arran"e the number as follows,

8?8?8?77?7 if 8?8 or 8?7 is one di"it add 0 prior to that < e"%

should be written as 0, - should be 0- etc../

Tae a number % 3-0'30- 3?3 double of 3?- -?- /

5rom ri"ht to left, eep the ri"ht most number as it

is and add the number comin" both side of symbol.ie. Ueep - as it is, add :0, add 3:'

1-Tae another e$ample 3

160' A 1'

&ant more tricks'8ll these trics ) learned are from the fantastic boo

secrets of mental math. This is one of the few boos

probably the only one/ that ) would carry with me

all the time. )t’s e$tremely cool to be able to perform mental calculations very +uicly, and you

can "et around it without bein" a nerd.

ere’s a list of what you can e$pect to learn from

the boo%• 8dditions and subtractions.

• 7asic and advanced multiplications.

• Rivisions.

• Vuessin" a number when it’s "ood enou"h/

• Wencil and paper math.

• ow to memorie numbers.

• Xany other trics that will impress your

friends.N ee more at% http%@@freestylemind.com@mentalN

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