# Quick Multiplication up to 20 x 20

**“I’m having trouble above 10×10.”**

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 20×20.

Today I am posting here on QuickerMaths.com, the method which I recommend to my students too.

**How to multiply up to 20×20 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, 6×3 = 18

**Step 4** – Add the product to the result of Step 2

Here, 190 + 18 = 208

Simple!! Isn’t it?

Another example, 17×19 = (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

I HAD A DOUBT IN THE CASE OF 20*17 AND 13*20…….? DIGIT VALUE ZERO CASE!

Thanks vineet 🙂

hey,is it any specific books available 4 this???????????????????????

plz tell,i need it…………………………………

its very nice n useful

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

THANKS!!! FOR THE GREAT TRICKS!

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

thanks khalid 🙂

how does it work for 3 digit numbers?

great job yaar…

Thumbs up to Sanjay Patel… His method works for any 2 digit and 3 digit numbers multiplication of anytype.. Thanks a lot..

absolutely amazing like that of serving on someone’s plate to fill one’s hunger. thanks.

Very nice and helpful. definitely stimulates one’s intellectual faculties.

great things r there…………ray

??? ???? ?? ???????? ?? ????

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

??? ??? ???…

Sanjay Patelji thanks a lot. This is the criss-cross method of vedic maths…i’ll soon post an article on the same!!

Dear, is there any another short cut then Matrix?

??

thanks

sir

thank you very much nandish

I would like to exchange links with your site http://www.quickermaths.com

Is this possible?

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

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

thanx NANDEESH H N

these tricks r really awesome

hy can u tell me D shortcut trick of multiplying 45*487

thanx

in advance

Same shortcut does not work everywhere.

One way of solving your problem is:

45*487 = 90*487/2 = 43830/2 = 21915

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

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

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

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

i want multiply up to 50*50

ahm ang hirap naman po.paano kung 63×17??ganyan po din ba na steps ang gagamitin???

THIS IS TOO MUCH TIME WASTE METHODS ………….

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.

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!