Quick Multiplication up to 20 x 20
“I’m having trouble above 10x10.”
This was a statement I heard many times while interacting with students preparing for competitive examinations including CAT. This was in response to my appeal to them to memorize tables up to 20x20.
Today I am posting here on QuickerMaths.com, the method which I recommend to my students too.
How to multiply up to 20x20 in your head?
Assumption: You know your multiplication table reasonably well up to 10×10.
I am trying to explain this with an example,
Say you want to multiply - 16 x 13
Step 1 – Add the unit’s digit of one to the other number –
Here, add 16 + 3 = 19
Or, add 13 + 6 = 19
Step 2 – Put a zero after the number (i.e. multiply it by 10)
Here, 19 becomes 190
Step 3 – Multiply unit’s digit of both the numbers
Here, 6x3 = 18
Step 4 – Add the product to the result of Step 2
Here, 190 + 18 = 208
Simple!! Isn’t it?
Another example, 17x19 = (17+9)*10 + (7*9) = 260 + 63 = 323
(10+a) * (10+b) = 100 + 10b + 10a + a*b
= (10+a+b) * 10 + a*b
==========
This can be extended to sums like 23 * 28
(20+a) * (20+b) = 400 + 20b + 20a + a*b
= (20+a+b) * 20 + a*b
So, 23*28 = (23+8)*20 + 3*8 = 620 + 24 = 644.
==========
& so on.by NANDEESH H N
Try for yourself. Let me know (by posting a comment below) if you liked it.
Click here for some more fast multiplication tricks
You may also like:
- Fast Multiplication Tricks
- Vedic Multiplication of two numbers close to Hundred
- Vedic Multiplication by 11
Who is behind QuickerMaths?
I am Vineet Patawari - PGDM (IIM Indore), ACA, B.Com(H). My passion for Mathematics, specially Vedic Maths encouraged me to start QuickerMaths
I believe that if trained properly using powerful tools like Vedic Maths, the immense intellect of human mind can be ignited instantly - find out more
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Recent Comments
Hello I saw the same trick in Vedic Maths India Forum (I think its Copy... – 14Jun13
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April 12th, 2012 - 20:08
hey,is it any specific books available 4 this???????????????????????
plz tell,i need it…………………………………
February 8th, 2012 - 15:14
its very nice n useful
November 2nd, 2011 - 21:16
Hi Nandeesh
can you tell me the above formula can be used in any two digit multiplication
and for three digit multiply what is the formula for ex: 839478*625
waht are short cut tricks for square, cube root, Division
October 2nd, 2011 - 12:05
THANKS!!! FOR THE GREAT TRICKS!
October 1st, 2011 - 16:26
another trick which suits to all two digit multiplication is
Eg-25*24
(5*4) multiplying one’s(here we remains with carry 2 ie 5*4=20)….0
now multiplying criss cross (5*2)+(4*2)+carry ie 2 is 20…..0
now multiply ten’s (2*2)+carry ie 2 is….. 6
the ans is 600
August 12th, 2011 - 16:54
great job yaar…
July 7th, 2011 - 13:59
Thumbs up to Sanjay Patel… His method works for any 2 digit and 3 digit numbers multiplication of anytype.. Thanks a lot..
June 14th, 2011 - 19:59
absolutely amazing like that of serving on someone’s plate to fill one’s hunger. thanks.
April 2nd, 2011 - 19:14
Very nice and helpful. definitely stimulates one’s intellectual faculties.
January 31st, 2011 - 12:35
great things r there…………ray
January 17th, 2011 - 13:20
??? ???? ?? ???????? ?? ????
235 *142=?
2 3 5
1 4 2
_____
????=5*2=10=0
1 ?????
????=?. ?? ?. ?? ???? ?? ?????? ???? ?? ???
=3*2 + 5*4=6+20=26
????? ?? ????=26+1=27=7 ,????? 2
?????=2*2 + 5*1 + 3*4
=21=????? ????=23=3, ??.=2
????=2*4 + 3*1=11+??.2=13=3, ??.1
???=2*1=2+??.1=3
????? ??? ???. ??. ?. ?
3 3 3 7 0
??? ??? ???…
July 15th, 2011 - 22:18
Sanjay Patelji thanks a lot. This is the criss-cross method of vedic maths…i’ll soon post an article on the same!!
December 1st, 2011 - 19:04
Dear, is there any another short cut then Matrix?
January 17th, 2011 - 12:40
??
November 13th, 2010 - 16:44
thanks
sir
October 7th, 2010 - 23:38
thank you very much nandish
October 5th, 2010 - 03:18
I would like to exchange links with your site http://www.quickermaths.com
Is this possible?
October 4th, 2010 - 08:56
I almost certainly would not have contemplated this was valuable two or three years ago, yet it’s fascinating how age evolves the manner you respond to things, many thanks for the article it really is great to discover something smart now instead of the typical rubbish masquerading as blogs and forums over the internet. Regards
September 27th, 2010 - 10:08
13*18 = (13+8)*10+3*8 = 234
23*28 = (23+8)*20+3*8 = 644
33*38 = (33+8)*30+3*8 = 1254
43*48 = (43+8)*40+3*8 = 2064
53*58 = (53+8)*50+3*8 = 3074
November 1st, 2010 - 13:38
thanx NANDEESH H N
these tricks r really awesome
hy can u tell me D shortcut trick of multiplying 45*487
thanx
in advance
November 10th, 2010 - 15:01
Same shortcut does not work everywhere.
One way of solving your problem is:
45*487 = 90*487/2 = 43830/2 = 21915
September 13th, 2011 - 20:39
another approach:
hy can u tell me D shortcut trick of multiplying 45*487
45*487=(50-5)*487=(487*50)-(487*5)= (487*100/2) – (no need to calculate it now)
= 24350-2435=21915…just trying it, in this way nos can be calculated mentally ofcourse with practice
June 29th, 2011 - 16:40
Hi Nandeesh,
Can u tell me short trick for 76*45
Bcoz above the nos are in 10′s or 20′s or 30′s.
Thank you
September 13th, 2011 - 20:42
76*45= simple use the guys method of criss-cross as explained in hindi.
or u can use 76*(50-5)=its very easy to multiply by 5 ain’t it
=(76*100)/2- no need to calculate it now= 3800-380=3420…ans
June 13th, 2012 - 21:04
13 *18 = 1*( 13 + 8 ) l ( 3 * 8 ) = 1*21 l 24 =21 l 24 = 234
23 *28 = 2*( 23 + 8 ) l ( 3 * 8 ) = 2 *31 l 24 = 62 l 24 = 644
33 *38 = 3*( 33 + 8 ) l ( 3 * 8 ) = 3 *41 l 24 = 123 l 24 = 1254
43 *38 = 4*( 43 +8 ) l ( 3 * 8 ) = 4 *51 l 24 = 204 l 24 = 2064
53 *58 = 5*( 53 + 8 ) l ( 3* 8 ) = 5 * 61 l 24 = 305 l 24 = 3074
September 26th, 2010 - 15:57
i want multiply up to 50*50
September 23rd, 2010 - 19:13
ahm ang hirap naman po.paano kung 63×17??ganyan po din ba na steps ang gagamitin???
September 22nd, 2010 - 10:48
THIS IS TOO MUCH TIME WASTE METHODS ………….
September 22nd, 2010 - 10:14
Very good!
(10+a) * (10+b) = 100 + 10b + 10a + a*b
= (10+a+b) * 10 + a*b
==========
This can be extended to sums like 23 * 28
(20+a) * (20+b) = 400 + 20b + 20a + a*b
= (20+a+b) * 20 + a*b
So, 23*28 = (23+8)*20 + 3*8 = 620 + 24 = 644.
==========
& so on.
September 22nd, 2010 - 12:17
Thanks Nandeesh!!
I have included your comment in the post itself.
Really glad that people like you visit this blog and contribute for everyone’s benefit. Thanks again!