Mental multiplication in 3 seconds

Want to knowhow to multiply some big numbers almost instantly in your head?

This trick is a great addition to add to your mental math toolbox.

Here is THE mental multiplication lesson playlist - progressing you through your mental multiplication.

[stevecampos]

My 7th grade math teacher taught me the trick for the square of numbers ending in 5, which I had opportunity to use on various occasions, including on my SATs, but I had not known about the trick for the other complementary numbers until today.(almost 50 years later). Better late than never. Thanks!

[debottamsarkar]

Wow what a great maths teaching . I have got full marks in maths for this teaching 😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮😮.

[riggsron]

I'm an old guy with memory issues. These tricks of yours are excellent exercises for me. Greatly appreciated.

[davidlewis]

You know I love dipping my toe into your lessons . I have to say though I think I have a fear of maths every time I look at your lessons my heartbeat goes crazy.

[zerotoleranceforsataniceli]

Hi there!
I didn't get your way easily & would struggle to remember the rule
But this is an older way of doing it & feels easier to remember, as you just round the big numbers up on one side & down on other side to nearest even number & so make them simpler to multiply in the tens & hundreds column & then just multiply the units as done in video .

63 x67 = 4221
same as
60 x 70 =4200 plus 3x7 =21
Total 4221

21 x 29 = 609
same as
20 x 30 = 600 plus 1x9 =9
Total 609

114 x 116 = 13, 224
same as
110 x 120 = 13, 200 plus
4 x 6 = 24
Total = 13, 224

etc
45 to power of 2
45 x 45 = 2025
same as
40 x 50 = 2000 plus
5 x 5 = 25
Total = 2025

[cheongyei]

Excellent trick...rare set of circumstances allow it, but great when the tens digits match and the ones digits add to ten. Thanks for sharing all you share.

[gwiyomikim]

Hmm...is it easier to remember these “tricks” or remember where I put my calculator.🤔

[SpaceWithSam]

Excellent content! Such a great explanation! Great work sir!

[RandomJ]

Me: bored
Youtube: Want to learn some cool math from Bruce in Finding nemo?
Me: Sure, why not.

[mjdedge]

I try round one the numbers up or down to the nearest 10 and adjust after that.
E.g. For 21 x 29; I do 21 x 30 = 630, then deduct 21 = 609
Or
Sometimes I break it into 2 simpler calcs,
E.g. For 21 x 29; I do 20 x 29 = 580, then 1 x 29 = 29; Then add the 2 = 609

[tipsybass]

What a great trick! In the 80s/90s, at least in my classes, we were drilled daily on our multiplication tables

[anoshgaming]

I living in India am learning western math
And this guy is teaching me vedic math

[wilfdarr]

“before you blast away in the comments...”
No no no, that's what drives the algorithm!😁

[liamoreilly]

Awesome way to work out multiplication of big numbers, wish we were taught this method at school and I would have enjoyed maths so much more, thankyou !

[oldpcgaming]

0:11 "I am gonna give you 3 seconds." Actually gives us 6 instead of 3.
Imagine if the teacher did the same during the examinations.

[dr.jamesolack]

I’m pushing 70 and I think these tricks are great! However, the one drawback is that the student doesn’t really understand WHY they’re arriving at the answer. That’s where doing the long version explains HOW you arrive at the answer.
For instance, why do you multiply the 10s unit by 7? Saying that you increase the 10s place by 1 then multiply the 2 numbers needs further explanation. Do you get what I’m saying? When you’re first learning math, you need to understand the WHY and the HOW of the computation.

[tommcgee]

I love being able to use tricks to do basic math faster than most people can type it into a calculator. I’m definitely going to practice this one more and add it to my mental box of tricks. Great job.

[lauramariawaugh]

Thanks that’s a good one. I really like how fast we get the squared answer.

[beckitibaldi]

Cool! Love when you teach mental math bits like this.🙂

[ALternaprof]

It works because if b+c = 10, then (10a + b)*(10a + c) = 100a(a+1) + bc.