@@tecmath Falmouth in Cornwall UK. It would have been the late 1950s. We were lucky we had a brilliant Maths teacher who made it a lot of fun. I still enjoy mental arithmetic, the reason I follow your channel on TH-cam.
I was taught the cross multiplication strategy a few years ago in 5th or 6th grade, but I’ve never heard of the rainbow strategy. Coming from a student, I like using the cross-multiplication when I’m taking a test or doing homework since it helps me multiply quickly, but I feel like if I get enough practice, I’ll be able to memorize the rainbow strategy and do large multiplication quickly in my head! Thank you so much for teaching me!
Definitely the cross multiplication Sir! Why on earth would they've not shown this way in school. Even keeps the interest cos of the simplicity! Great job as always 👏
Both these are pretty much the same method, one is horizontal and the other vertical, but I think the cross multiplication version is easier to keep track of.
I prefer cross method of multiplication shown in the video because it solves problem from right to left and this prevents minute errors (like forgetting to add carrying number) and it also saves us from hassle of erasing and rewriting new answers (like you had to do in rainbow method). [DiowE]
I multiply place values sideways. Ex. 12x31(12×30 or 12x3=36and bring your 0 back in. Then 12x1=12. Add 360 and 12= 372 For 43x52 (43×50 and 43x2. Add answers = 2150+ 86= 2236
I prefer the rainbow method. I feel it's better when you need to approximate products quickly. Rainbow method isnt how I do it my head though. I like using the grid method more when multiplying because it extends to 3 digit numbers easier.
Happy Christmas Josh and my condolences to you and all teachers in your country on the poor children in Tasmania at such a hard time for this to happen
first multiplication, method 2 is how we learned it in school in the Netherlands. So what is the "standard way" of multiplication for you? 10x31 + 2x31?
From what I can see both processes are using the technique (vertical and horizontal). The horizontal one at first seems messier because you have to erase/rework where there are carries in other parts of the calculation. But if you calculate from right to left as you do for the vertical ones, then less mess and essentially doing the same thing.
I prefer the way I did it. I multiplied the tens in the first number by the entire second number. Then I multiplied the units in the first number by the entire second number. Then added them together. 43×52= 40×52= 2,080 3x52=156 2080+156=2,236 For me it was easier to see as it is easy to multiply a two digit number by any of n2-n9 and add a 0 at the end. Then just multiply the remaining units with the other two digit number. Perhaps I am just more practiced. tens by tens plus tens by units plus units by tens plus units by units Left to right rather than backwards that they teach in school. But it is all the same thing. I just cut out the middle by doing tens by whole number plus units by whole number example 64 x 83= 60×83=4,980 4×83=332 4,980+332=5312 I just thought about it. This is how the operations would be complete to multiply using the mechanical Curta calculator. Or at least one of the methods.
I like the cross method my teacher didn't liked it when I tried using a calculator on a very simple equation so I'm starting to learn stuff the first time again
You're giving me knowledge, sadly i can't support financially and all I can do is like, subscribe and share your vid on my friends. Thank you so much. Keep on doing more. Love from Philippines
Really like this.. now I need to analyze this to see WHY it works. But that’s just because I want to maintain my NERD status. PS. I prefer cross method.
How about doing the three stages (100s, outside 10s, inside 10s, 1s) as four different rows and sticking an appropriate number of zeroes at the end? Then you can add up the four rows and won't have to rub anything out. Doing all the multiplication tasks first and then adding everything at the end also means you don't have to swap tasks hopefully leading to a slightly faster result. What do you think?
@@tecmath I believe for the larger numbers it requires writing out lines of results to add, but with cross multiplying it's mainly mental? Anyway it's true both methods use the same formula. However I'd appreciate any further insights u have and it was worth doing another video on them
excellent multiplication techniques, students can certainly make use of these
Thank you
They can
I was taught cross multiplication in school in the 1950s, seems normal to me. Love your channel keep them coming, thanks.
Wow you are in your 70's :o
@@FatenElAli24 not quite.
That is cool! Where was that?
@@tecmath Falmouth in Cornwall UK. It would have been the late 1950s. We were lucky we had a brilliant Maths teacher who made it a lot of fun. I still enjoy mental arithmetic, the reason I follow your channel on TH-cam.
@@stonkeng how old are you?
I was taught the cross multiplication strategy a few years ago in 5th or 6th grade, but I’ve never heard of the rainbow strategy. Coming from a student, I like using the cross-multiplication when I’m taking a test or doing homework since it helps me multiply quickly, but I feel like if I get enough practice, I’ll be able to memorize the rainbow strategy and do large multiplication quickly in my head! Thank you so much for teaching me!
They're effectively the same. Rainbow multiplication is just writing it in a single line.
Definitely the cross multiplication Sir! Why on earth would they've not shown this way in school. Even keeps the interest cos of the simplicity! Great job as always 👏
I'm sure you get told this a lot, but you're genius in your teaching methods. Thank you immensely. Learn something new every day. 😅
Thank you Cassandra.
your videos never stop to astonish me.
Thanks Vijay.
cross multiplication is my favourite method! Excellent video! Thank you for making math easier!
Thanks. Go the cross method.
Why was I never taught this method? I am actually enjoying learning this math. Thank you.
Thank you always looking for fast math videos for competition.
Fantastic method! I'm really looking forward to the rest of the series.
In reality, they are both the same methods just expressed in different ways. Well done thank you!
this changed my life
The way you have such a calming voice is really enjoyable to watch your videos and easier to learn with your tricks.
Thanks. I save my yelling during lessons for real life! (jokes... I never yell!).
Rainbow has the back tracking, messy, cross is clean as hell.
I like cross so much more!
Both these are pretty much the same method, one is horizontal and the other vertical, but I think the cross multiplication version is easier to keep track of.
Yep. You could see as the numbers were coming out the similarity!
@@tecmath I love your channel, you have helped me understand numbers in general way better, thank you.
I agree with you
i prefer the cross multiplication, i really really enjoyed the video thank you!!!
I prefer cross method of multiplication shown in the video because it solves problem from right to left and this prevents minute errors (like forgetting to add carrying number) and it also saves us from hassle of erasing and rewriting new answers (like you had to do in rainbow method). [DiowE]
You could do rainbow right to left.
Cross multiplying can also be done left to right which I prefer
They are basically the same method just written different. That means you can do the rainbow method backwards.
I agree with the comment of Faith. Careful home training free from useless waste and a school system that has math teachers like Josh.
I was taught the cross multiplication. Awesome explanation
I multiply place values sideways. Ex. 12x31(12×30 or 12x3=36and bring your 0 back in. Then 12x1=12. Add 360 and 12= 372
For 43x52 (43×50 and 43x2. Add answers = 2150+ 86= 2236
I don't know which I prefer, but I've been waiting a long time for this. Now I have to practice it for a while. Thanks!
For mental, rainbow flows better, but needs more memories to hold numbers in the head is a struggle.
i like the cross multiplication. we can do 3, 4 or as many nos. as much we want, quickly! and one more thing, ur channel is really amazing!👌🏻
I like the cross multiply method best.
I like the second method as it’s basically what I learned in school but with a nice twist.
It can be extended also easily for any multiplication... th-cam.com/video/LgJ5bNHBbD4/w-d-xo.html
I prefer the rainbow method. I feel it's better when you need to approximate products quickly.
Rainbow method isnt how I do it my head though. I like using the grid method more when multiplying because it extends to 3 digit numbers easier.
Hello Josh, can you do a video on linear equations with integral coefficients please
I cannot believe I just learned this! I prefer the cross multiply method!!
Good to hear! I agree!
Cross multiplication cuz it's easier and thank you for these videos
Thanks for the vid. I might be an outlier but the rainbow method works for me.
Excellent. Hope children can understand
You such a great teacher. Thank you for the videos. Keep them up!
Thanks!
Can you make videos on calculus such as limits and differentiation and integration please
Happy Christmas Josh and my condolences to you and all teachers in your country on the poor children in Tasmania at such a hard time for this to happen
Thank you and Merry Christmas to you.
What happened in Davenport is heartbreaking. Those parents, teachers and classmates must be devastated.
@@tecmath Certainly and Amen Josh
Woah! I really liked the rainbow method
Today’s content was amazing.
Great method Josh!
first multiplication, method 2 is how we learned it in school in the Netherlands. So what is the "standard way" of multiplication for you? 10x31 + 2x31?
Cross is definitely my favorite
I prefer the cross multiplication method. Great video, keep up the great work!
Thanks. Another vote for cross!
You made a mistake on your caption,I think you meant "Multiplication methods that are faster than you learnt at school"
Thanks Flex. Fixed.
I definitely prefer the cross method but it's great to have more than one option. 👍
The cross method totally!
Excellent upload 👌 👍 Thank you for sharing 😋 👌 😊 😀 👍
From what I can see both processes are using the technique (vertical and horizontal). The horizontal one at first seems messier because you have to erase/rework where there are carries in other parts of the calculation. But if you calculate from right to left as you do for the vertical ones, then less mess and essentially doing the same thing.
2:45 I personally like both. Depending on how it is written on the paper, just so I don’t have to rewrite the problem.
I prefer the way I did it.
I multiplied the tens in the first number by the entire second number.
Then I multiplied the units in the first number by the entire second number.
Then added them together.
43×52=
40×52= 2,080
3x52=156
2080+156=2,236
For me it was easier to see as it is easy to multiply a two digit number by any of n2-n9 and add a 0 at the end. Then just multiply the remaining units with the other two digit number.
Perhaps I am just more practiced.
tens by tens
plus
tens by units
plus
units by tens
plus
units by units
Left to right rather than backwards that they teach in school. But it is all the same thing.
I just cut out the middle by doing
tens by whole number
plus
units by whole number
example
64 x 83=
60×83=4,980
4×83=332
4,980+332=5312
I just thought about it. This is how the operations would be complete to multiply using the mechanical Curta calculator. Or at least one of the methods.
I like the cross method my teacher didn't liked it when I tried using a calculator on a very simple equation so I'm starting to learn stuff the first time again
You're giving me knowledge, sadly i can't support financially and all I can do is like, subscribe and share your vid on my friends. Thank you so much.
Keep on doing more. Love from Philippines
Thank you for your kind words.
God bless you good sir.
I prefer the regular way because I get lost in the steps. But I do like the percents to numbers switch in your other video
Hello sir,
Thanks for all you do!
I was wondering if you could do a act math prep video?
It would help so much
"Multiplying faster than a rabbit..." I had to stop for a second 😂
you're the goat tecmath
A goat. Not THE goat.
I like the cross method too.
Excellent. Thank you.
this is fast and easy, love it
I love the Rainbow one
wonderful, thank you! I like the cross method best :)
I like both of them: they are similar ways that don't require as much calculation.
The funny thing... the calculation is the same as standard long multiplication - except the addition is more compressed.
Thank you.
You are my life savior in account
Thank you for watching.
thank you
in Holland, the right hand cross multiplication is taught from grade school :)
Really like this.. now I need to analyze this to see WHY it works. But that’s just because I want to maintain my NERD status. PS. I prefer cross method.
Thanks!
I'll give you a hint.
For all of these we have the hundreds digit (T x T), tens digit (T x U +U xT), units (UxU).
I like the cross method.
Thank you so much..
Cross multiplication (because the rainbow method really only seems to work easily with numbers less than 100)
Amazing Tricks
Guess I’ll just stick with the old school method, but it’s cool for the younger minds!
Thanks for vids , how about making a videos about roadmaps for learning mathematics ?
How about doing the three stages (100s, outside 10s, inside 10s, 1s) as four different rows and sticking an appropriate number of zeroes at the end? Then you can add up the four rows and won't have to rub anything out.
Doing all the multiplication tasks first and then adding everything at the end also means you don't have to swap tasks hopefully leading to a slightly faster result. What do you think?
That is how I would think about it mentally.
I find cross multiplication stops all the need for that.
I was so surprised how easily he did it i went to check on a calculator the guy is never wrong
Thank you thank you
I recommend for me that the rainbow multiplication is better for me
Cross multiplying work's best for me
This is the first video that I've actually known the method before.
Both are good but I like the rainbow
:)
வாழ்த்துகள் ஐயா 🎉
பயனுள்ள பதிவு
நன்றி
Awesome techniques but I think cross multiplication method for me!
I agree
Multiplying faster than a rabbit.😂 if you know you know
very good !!!
Agree
thx alot
I like them both equally but when it comes to large numbers I prefer the rainbow method
Interesting! They are essentially the same, and either can be run left to right or right to left.
@@tecmath I believe for the larger numbers it requires writing out lines of results to add, but with cross multiplying it's mainly mental? Anyway it's true both methods use the same formula. However I'd appreciate any further insights u have and it was worth doing another video on them
It helps break down what is happening when we multiply, but it seems too confusing for those beginning double digit multiplication.
Excellent. Please what app you use?
on 0:45 how do you know how many spaces to put down after multiplying the numbers in the front?
Hello Josh!
Can you do a reverse percentage video please?
The rainbow method is like FOIL with numbers
I use a different method. For example 12 x 36. I first do 36 x10 so i get 360. Then I do 36 x 2 so i got 72. And then i add them both. To get 432
I would do 12 x 31 different by doing 2 x 31 (62) + 10 x 31 (310) equaling 372
Why did they not teach us this in school. I would aced everything in ten minutes
Fish are friends, not Food...
The second way suits me better.
Cross multiplication is my choice.
This method is harder to me to do than what I'm used to
Wait ! So you are telling me that the Cross multiplication method was not the common method used in schools?
Cross multiplication
10*31=310 & 2*31=62 => 310+62=372