Your fingers are secretly a powerful calculator
ฝัง
- เผยแพร่เมื่อ 22 ต.ค. 2022
- What sorcery is this?! You can easily multiply numbers from 6 to 10 just by counting your fingers. #math #maths #mathematics #shorts
Subscribe: th-cam.com/users/MindYour...
Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas!
If you purchase through these links, I may be compensated for purchases made on Amazon. As an Amazon Associate I earn from qualifying purchases. This does not affect the price you pay.
Book ratings are from January 2022.
My Books (worldwide links)
mindyourdecisions.com/blog/my...
My Books (US links)
Mind Your Decisions: Five Book Compilation
amzn.to/2pbJ4wR
A collection of 5 books:
"The Joy of Game Theory" rated 4.2/5 stars on 224 reviews
amzn.to/1uQvA20
"The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" rated 4/5 stars on 24 reviews
amzn.to/1o3FaAg
"40 Paradoxes in Logic, Probability, and Game Theory" rated 4.1/5 stars on 38 reviews
amzn.to/1LOCI4U
"The Best Mental Math Tricks" rated 4.2/5 stars on 76 reviews
amzn.to/18maAdo
"Multiply Numbers By Drawing Lines" rated 4.3/5 stars on 30 reviews
amzn.to/XRm7M4
Mind Your Puzzles: Collection Of Volumes 1 To 3
amzn.to/2mMdrJr
A collection of 3 books:
"Math Puzzles Volume 1" rated 4.4/5 stars on 87 reviews
amzn.to/1GhUUSH
"Math Puzzles Volume 2" rated 4.1/5 stars on 24 reviews
amzn.to/1NKbyCs
"Math Puzzles Volume 3" rated 4.2/5 stars on 22 reviews
amzn.to/1NKbGlp
2017 Shorty Awards Nominee. Mind Your Decisions was nominated in the STEM category (Science, Technology, Engineering, and Math) along with eventual winner Bill Nye; finalists Adam Savage, Dr. Sandra Lee, Simone Giertz, Tim Peake, Unbox Therapy; and other nominees Elon Musk, Gizmoslip, Hope Jahren, Life Noggin, and Nerdwriter.
My Blog
mindyourdecisions.com/blog/
Twitter
/ preshtalwalkar
Instagram
/ preshtalwalkar
Merch
teespring.com/stores/mind-you...
Patreon
/ mindyourdecisions
Press
mindyourdecisions.com/blog/press - วิทยาศาสตร์และเทคโนโลยี
when you have to multiply 1828×9273 and the teacher starts throwing gang signs
bro doing the fireball justu
222,2
thnotthliker
expecting answers, summons Madara
@@XBGamerX20
Smart people aren't calculators, buddy.
Unless if you have a pen and paper to do some long division, people need a method to do this.
@@Mike-lx9qn its a meme bruh
imagine a professor is teaching a calculus class and pulls out his fingers to multiply
Lol
LOL
Me: Sir don't you know how to multi-
Prof: MIND YOUR BUSINESS
@@Luffy_wastaken lol
Savage
Kid named finger:
Finger, put your math away, finger
hahahahaha
I'm not doing calculus with you right now, Finger
kid named "math finger"
Kid named math💀
this seems like it would be harder to do than just multiplying normally
You'd need only a quarter of the multiplication table, though 😊
if u multiply numbers alot u just naturally memorize it
@@konstantin.v do you mean that this method only covers a quarter of the multiplication table?
@@noobatredstone3001 , that, too 😊
@@konstantin.v isnt that like bad since you cant get the other 3/4ths (also you cant even multiply 5x4 with this, although its arguably easy)
For any integer a and b where 6 ≤ a,b ≤ 10, then
The "touching fingers and the ones below" part translates to
(a - 5) + (b - 5)
which then multiplied by 10 because it's placed in tens place, becoming
10 × ((a - 5) + (b - 5)) ... (i)
The "above touching fingers" part translates to
(10 - a) × (10 - b) ... (ii)
Adding (i) and (ii) together we get
10 × ((a - 5) + (b - 5)) + (10 - a) × (10 - b)
= 10 × (a + b - 10) + 100 - 10b - 10a + ab
= 10a + 10b - 100 + 100 - 10b - 10a + ab
= (10a - 10a) + (10b - 10b) + (100 - 100) + ab
= ab
which is the product of a and b
---
Just my view on this
👏🏻👏🏻👏🏻👏🏻
Neat
Gr8!
r/theydidthemath
I wish I could upvote you more. Thanks for doing the proof so I don't have to. Super clear and detailed. Well done!
It's incredible that anyone would choose this rather than memorizing their multiplication tables.
It’s way easier
@@R1CK4STL3YGAMINGHOLYY its preferences,but i Can Try convincing you when it comes to mathematics,using this method takes too much time,not to mention counting,i Reccommend you to slowly build up your mental calculation from 1-10 like the multiplication table as doing them is easier,an easy way of doing this is(assuming youve memorized the table)is when theres a number thats past 5 i usually start off at the half of the number and Multiply my way up,it saves alot of time,it makes the multiplication table look like 2 times easier so i encourage u to do it
Agreed, this takes like 10 seconds and times table takes less than a second, doesn't seem like much but if you're in an exam and there's a whole load of questions having many multiplications, obviously the times tables is going to be better
Me
I use this method since I was in kindergarten. I'm very bad with rote memorization so it helped me so much.
I got the formula
It is 0.25(x - |x - y|*-1 + y - |x - y|) + 0.25(x - |x - y| + y - |x - y|*-1)
Remove the plus to get 2 separate formulas, but combining it cleans it.
Also, remember to multiply 0.25 by 2 else it will give you half of the formula!
When you don't have fingers remaining to add:
then it's 0
Who made it through school without having to memorize every single digit multiplication table?
That is the point!!!!
Does "memorising how to do extremely simple multiplication" count as memorising the multiplication tables?
@@Doktor_Vem sort of. I was very good at understanding the fundamentals to solve harder problems but I had a math teacher that liked speed pop quizzes. From 1 to 100: 15 seconds to write all prime numbers, the other quiz was 2 minutes to write all their prime factors.
I'm going to be brave and say that subscribers to this creator won't include the low ability students
I did memorise, but tend to forget them now
Me who can finally multiply without using my brain power: thank u
What sorcery is this?! But seriously what is this, why does it work?
It's actually pretty simple. The important numbers for what we're calculating is the number of lower fingers, including the ones that touch, so for the left hand we can call that number x and for the right hand we can call that number y. With x and y defined like that, what we're calculating is (5+x)(5+y) which equals 25+5x+5y+xy. But, in calculating the product of the higher fingers, we get (5-x)(5-y) = 25-5x-5y+xy. The total product and the product of the higher fingers only differ by 10x+10y=10(x+y), which is exactly the quantity we get using the sum of the lower fingers as the ten's place. So in sum, the trick works because 10(x+y)+(5-x)(5-y)=(5+x)(5+y).
@@corlinfardal9246 Thank you!
69th like :)
@@R1CK4STL3YGAMING what now? lol
@@SuperYoonHo >:(
this is very interesting!
it may not be practical, but I think it can evoke curiosity and love for math, especially in children
could you do a video on why it works?
Yes!
I count faster than I'd do this Lmao
Call a, b are 2 positive integers such that 10 ≥ a, b ≥ 6.
Base on the trick:
The first part is to count the number of fingers under those 2 fingers and include them, then multiply by 10:
10[(a-5)+(b-5)]
The second part is to count the remaining fingers of both hands and multiply them:
(10-a)(10-b)
Sum it up and we have:
10[(a-5)+(b-5)] + (10-a)(10-b)
=10(a+b)-100 + 100-10(a+b)+ab
=ab
This proof is true for all integers, but to make the trick easier to use, a and b must be in the range above so we can just deal it with non-negative integers and can use the trick by both hands.
elementary algebra
Multiplication table is evil, made me miss so much
Instructions unclear; got shot in Compton
My father told me when I was a kid, that he knew someone who could multiply using hands. Now i know how to do it. Amazingly it works for "5" as well, you only need to imagine having a zeroth finger.😄
6th*
@@Marvin-ho1vo 0th finger would have a factor of 5, 6th finger would have a factor of 11. It wouldn't work properly then.
'We touch the fingers of 6 and 9"
Don't say it don’t say it don’t say it I CANT CONTROL IT-
Noice.
It can maybe u didnt multiply above the number
I wish the trick goes beyond single digits
10 is a double-digit. :p
It's ok i'll just study tables and multiply in the OG way
Instead of doing this bs I'll just memorize the 15 results.
6x6, 6x7, 6x8, 6x9, 6x10, 7x7, 7x8, 7x9, 7x10, 8x8, 8x9, 8x10, 9x9, 9x10, 10x10
That's all.
There’s 25 actually
@@noobatredstone3001 You're wrong, I literally put all combinations there.
@@Yusso Ah, I forgot that the order of the factors does not matter.
@@Yusso except you used 5 instead of 10. Yes, there's 15 of them, but those aren't the combinations. :-)
@@Yusso sure the "concept" is the same, but you STILL have not used the 6 to 10 that would've been "literally [...] all combinations"...
And what was that about "1 to 10"?! Of course it's not that, if it were that it'd have been 55 combinations, not 15... -.-
*TIL:*
Hand multiplication exists.
Theres also a specific hand technique for multiplying by 9 (works only up to 9x10 tho)
I would rather memorize the multiplication from 1 to 10 over this 1000%. I already memorize to the point its a reflex and doing this is hell
imagine sitting in class and some kid just starts throwing gang signs trying to figure out 8x4
@@theonewhocaredandasked9126 8×6*
As my father once said "learn your damn multiplication tables, boy!" right before he beat my ass
Instructions unclear, can’t multiply any two numbers less than 6
6*6 also does not work.
@@rockingamingwiththesahit2145 touching fingers and below is 2 fingers, so that gets us a start of 20. Then you got the pair avove, 4x4 is 16. 20 + 16 is 36. 6x6 is also 36, so it does work
@@rockingamingwiththesahit2145,
It actually does. By the method, it would become 20 + 16 = 36
@@rockingamingwiththesahit2145 it does work, now put 6 finger on 6 finger and count them, you'll have 2 now whats 4x4? it's 16 the one goes to 2 making it 3 and the 6 stays, so you have 36. and 6x6=36
9 x either 1,2,3,4,5,6,7,8,9,10 will always result in an answer that all the integers will add up to 9
For ex: 9x2 = 18. 1+8=9
a way simpler trick is to label your fingers 1 to 10 from left to right. bend the finger with the label of the number you want to multiply by 9. the number of unbent fingers to the left and right of the finger you bent are the digits of your answer.
for example, to multiply 9 x 5 you'd bend the 5th finger. you'd have 4 unbent fingers to the left and 5 to the right, giving you 45
u shoulda uploaded this apr 1 to troll people
This is not even a trollage it does really work if you do it correctly
@@flacsomtodosclas2165 yeah! this IS maths
We touch the “fingers” of six and nine
Kid named six: 😳
Kid name nine: 😏
For the zero people who care: here's a simple proof
The first number you select will be (5 + x) where x is an integer 1-5. The second number will be (5 + y)
Now, x is the number of fingers on one hand below the line, while y is for the other. You can portray the remaining fingers on each hand as (5 - x) and (5 - y). These will be multiplied together. The fingers below the line will be multiplied by 10.
Therefore you have the equality
(5 + x)(5 + y) = 10(x + y) + (5 - x)(5 - y)
Foil gives you
25 + 5x + 5y + xy = 10x + 10y + 25 - 5x - 5y + xy
The 25 and xy can be cancelled from both sides
5x + 5y = 10x + 10y - 5x - 5y
Combine like terms in the right and
5x + 5y = 5x + 5y
Therefore it will always work
I like how this guy used 6 x 9 as one of the calculations and 42 as one of the result.
Now i realise why they taught us multiplication table.
Just memories the table’s 😂
What about 5x5?
=0
500
Now this is what my teacher calls finger math
Him : 6 * 7 = 42
Me : 312
😂😂same
7 x 8 is as 7 x 4 + 7 x 4. It is 56
I feel like it would be way faster to just do it normally
You feel bro it iss ‼️
Hardwork has no substitution
Im going to remember table now
This is what I imagine if a baby could speak properly and tried to explain to us how finger counting is superior.
I like how you still have to multiply 2 x 3 to figure out 7 x 8
Interestingly enough, if we could visualize placing the "top" fingers over each other (say, one hand horizontally and the other vertically), there'd be a way to find out that 2x3 by counting the points of intersection instead of multiplying numbers. :-)
Every one gangsta until 11×11
Nah, dude.
11 x 10 just move the decimal to the right one digit, 110,
Then add 11, 121.
REMEMBER IT 🤬
just learn the table man
I tried doing 6 times 6. And realised that I have one finger less than everyone else! Because I could only count two touching fingers and no fingers below. But I needed a 3 🤯!
dont worry you have the same number of fingers as I do😂
you count the two touching fingers and get 20
then when you count the remaining fingers you will get 4×4=16
you add them and get the answer
20+16=36 (=6×6)
the 6×7 example in the video follows a similar process
My dad taught me a similar technique as a kid it was really a life saver
"what if you have no fingers?"
Very useful when you don't know the tables till 10.
or a kinda different way to do this but same technique is having your hands side by side palms facing you, the innermost fingers starting from the pinkies are 6 and so on till the thumbs which are 10. have the numbers/fingers you are multiplying up and the ones you arent down. count the fingers that are up (you should have all the fingers from 6- the number you are multiplying like if youre multiplying 6 and 8 your left hand should have only your pinky up and then your right hand should have ur pinky, ring finger, and middle finger up) the amount of fingers up is your tens place and then count the fingers that are down and multiply the amount on your left hand and the amount on your right hand thats your ones place. sorry for the confusing explanation its hard to explain without using pictures
For 6 × 6, make sure you add the numbers
If only I had learned this in 3rd grade.
i learned this in kindergarten, happy to know my teachers were good ones
Nice thumbnail you got there, so perfect.
I tried to count to 144 using a dozenal base-12 numbers using the lines of fingers and not a thumb because the thumb has 2 lines. Just count the bones from the fingers that are separated from those lines.
If you count to twelve already. Do the same on the other hand and skip count from 12 to 144.
Hope you understand 👍
Clever but seems easier to just remember the times table old school way
For 6×7 I just distributed the 1 on top of the 3 and added it to a 4 in order to get 42.
Teacher: rocked
Student: shocked
😂😂😂😂😂😂
Given two natural numbers a, b, such that 0 < a,b
This is something I'd forget how do to everytime. Just memorize it. 😃
It would have been easier to do daily arithmetic in mind with Base 12 with factors 1, 2, 3, 4, 6, 12. Or.. easier with Base 2 (Binary), as multiplication tables are very intuitive for us in Base 2.
This is gonna help me so much when I'm uncertain on a question like 7×6
I'd rather keep my dignity
Teacher: Who can solve 18x32?
Me: *Uses Math Multiplication Jutsu*
The Deaf Kid: Why does he want to paint billy's toes green?
Great way of making math harder
When the teacher says the test is done without a calculator:
i love doing it with my finger!! this really helped me multiply
I'd love to send this video to my past self
I swear I've learnt this method 5 times now and Everytime i need to calculate i just forget about it and do it in my head.
Super technique thanks for uploading 😊
Instructions unclear, I just summoned a giant talking ninja frog
Thank you I will definetely use this in my upcoming exams.
Memorizing the trick is harder than multiplying it manually
You are a life saver omg thank you ur the best❤
"...or you could memorize your tables!"
This is unnecessarily complicated for basic arithmetic.
For some single multiple number, I'll just memorized them thank you
I don't need this I memorise all
My grandma use to do this trick at school.
That just seems so much more complicated.
Bro i ain't gonna do a jutsu just to multiply 3*3
I’ll stick with my multiplication table
uhh i think i'll stay on mine
Should have told my brother who had a multiplication contest
In school we had to memorize all products between two factors from 1 to 10.
I had to memorize products all the way up to 12.
i wish there is a single finger trick that helps with high level math. These kinds are fun and especially so to find proofs why it works, but not quite practical unless u never graduated from grade 3 (same for the multiples of 9 trick). Imagine doing some finger trick that helps with power or square root, which is probably the simplest thing we can't do (or can't bother to do) on top of our head.
i wish i knew this before spending 8 hours of my time memorising all the times tables till 12
I’ll stick to my 9 times table
I learned this trick from another guest in a camping place in France this summer.
When u use this trick your exam times end already..lol🤣
People who have 6 or more fingers💀💀
I am gonna count with 69420 x 69420 No Jutsu
That is good how you teach some of usis like to know some numbers 😊😊❤❤ good teacher
4*7 walks in
Interesting but I had a math teacher with a different tactic. Pop quizzes throughout the year. Pencil paper: you have 15 seconds to write all the prime numbers from 1 to 100. The other pop quiz you have 2 minutes (maybe 1), I forget from 4 decades ago, to write all the numbers from 1 to 100 and their prime factors.
I mean, if it only works.for numbers less than 10, multiplication isn't really that hard is it?
This is harder than multiplying normally
The amazing part is if people need to use their fingers for low numbers like that.
Sooo, it works from 36-100 only, for one person
Yup, just a quarter of the multiplication table
Everybody gangsta till you gotta multiply 2 digit numbers
10(a+b)+(10-a)(10-b)-100
how to multiply numbers:
count the touching fingers and the one below them
let's *multiply* the number of fingers on the left hand by the number of the fingers of the other hand
Just memorized multiplication from 1 to 10 when you will be in 4th grade.
Yeeees, finally someone explains multiplying using fingers!!