Mental Math Tricks - How to multiply in your head!

How can you multiply in your head? Mental maths is easy - using this trick to reprogram your brain to multiply quickly and easily. This lesson shows you tips on how to multiply faster than ever!

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Closed Caption:

should i welcome to the take math
channel when we have a look at this
video is a very special video we're
going to be looking ahead and multiply
mentally and multiply big numbers
mentally so bear with us you might look
at the party tonight
so hey I can do this much faster with a
pen and paper but this isn't a better
owner multiplied with a pen and paper
this is actually trying to get you
eventually multiplying mentally which is
where the real i challenge lies a lot of
the time
okay so I'm gonna start this off with an
example let's say I get you doing this
one
what is our analysis you want to start
off with 3021
and we're going to times that by three
so the answer that you should get for
this is 9063 did you get an answer
you know what I reckon you probably did
and i'll show you how i reckon you
probably got there yeah I think you
probably got that
ok i would expect the way you've done
that you would do this because you're
doing this a written method you would go
one x rays 3 2 times 3 is 6 30 times
nothing is nothing
three times three is nine ok now look
that's nice and easy if you're doing it
on Piper
but it does become a little bit hard or
all of a sudden when you're not able to
actually see the numbers
ok and in a second i'm going to actually
are
I'll give you one without the numbers
then i'll actually right at the animal
work three
now your mind might want to get ready
program because i do this slightly
differently instead what we tend to do
is we tend to work at questions
this way from right to left
where is what we actually think of them
as we actually think about them this way
ok when I think about this number being
three and 60° and not theirs and we
think about this is not theirs and 63
and this is the challenge with
multiplying matrices to turn the wire
around that you currently
work your multiplication so you think
about them in the way that you actually
think about them
ok in their particular my rather than
actually working against the way your
mind actually wants to work
ok so the way that I would do this is a
little bit different than this is what I
mean with her we would have to change
the way that we are at work we do this
three times by three but instead what we
would do is we would go three times
three is nine zero three times two is
six three
ok and we're actually working this in
the way that we actually you know you
that you think the number
okay i'll give you another example
so i'll rub his hair and then I'm going
to ask you for example to work out what
is a 50 1230 1 times 3
ok Cee it's quite hard if you are if
you're not used to doing in that
direction so the answer by the way is a
hundred and fifty 3693 ok let's are all
right there
so let's want to write the questions and
first 50 1231
it was x 3 so the way we do it is this 3
times 5 is 15 we put that dear
so we going from left to right five-time
straight straight straight onto one his
three two times three is six straight
times 3 is 9 1 times 3 is 3
you see we were working this way and
this is the trick to mental calculations
mental multiplication so I know what's
going to happen i'm gonna start getting
probably comments people sign this is
hard this is not what I'm used to it
because it's not what you're used to but
then again
you also might realize that the method
you're used to is no good for mental
multiplication so this is it does take a
bit of practice but this is the way to
do it mentally
this is well one of the ways to do it
mentally
so I'm going to give you a another one
yep
what about we deal with a hopefully do
pretty good with this
what about we do a different one here
what about we do something sound like a
60 1413 i'll write that number down 61
there's and 413 and all times that
number by for their from now on
rather than sign them i'm going to
actually you know so they had actually
running down your mark out four times 6
is 24 1 times 4 is 4 then the 16 y SE
hanging to deal with this
Carrie hear what you say I don't even
know what just went on to explain here
slightly what the problem will be here
ok so what we're doing this we have a
bit of a problem because what we do is
we have 6 times 4 is 24 1 times 4 is 4 4
times 4 is 16 y/o second that means
we're going to have to carry something
so we're gonna put the six they're going
to carry the 1 so this is going to
become a 5 1 times 4 is 4 and then 3 4
12 so too is going to go there and the
ones going to get carried across and
that will also become five
yeah the carrying all the sudden can
become a bit of a problem when we talk
about mental calculation because Carrie
numbers in your head tends to throw
things a little bit
what we tend to have to do is we have to
carry as we go but we also have to start
doing this little thing which i call pre
carrying ok
it just involves glancing at the next
party or answer to work out what what
your you can't all be our show you what
i mean by this
ok then we'll go through a couple of
examples with this
so say for example i do our
this one here 30 1616 and our times this
number but for ok
I work through how this concept of pre
carrying works
so first off we do this three times for
and we get the answer of 12 but before I
10-12 look at the next part of the
answer
I'll go 1 times for the answers below 10
I'm not going to have to carry anything
so i can put them or 12 if I did have to
carry something I carried across and put
that as part of on it and you'll see her
and me on this one it's right near 1
times 4 is 4 so i quickly look at the
next part and 64 2424 I'm gonna have to
carry this - okay so this is what I'm
gonna pre carry on it pretty carried
across so 1 times 4 is 4 plus X 2 from
the next part is going to be 60 k or i
will see here we go with that
so the next one is six times 4 is 24
we've already written down that so they
were pretty carried that the number
afterwards is 1 times 4
we're not gonna have to carry the cross
so i can just put down at four
okay for one times four
I look at the next part ok
and that's 6 times 4 is 24 get the pre
carry two across
ok so one times four is four plus two is
six ok did you get that
and then the last part well that's just
going to be whatever that units part was
going to be united six for 24
so that's why with that four guys then
but this is the concept of pre carry
ok and it's a the biggest part of this
trick is to be able to get the pre carry
right
ok we can get the pre carry right you're
really on the white getting these
mentally are correct
so what about i give you another example
ok
i will write this one dear what about
for instance 20 1613 and we times that
by five
ok just going to make sure i'm gonna get
some numbers where we are going to have
to carry and pre carry things across ok
so first off what we do
going from left to right through x 5 is
10 and we look at one times five
no pre carry so i can put my team ok
Oh put a little tip - oh that's what
I've done it ok 1 times 5
ok that's going to be five and i'm gonna
have to pre carry six times while
30 on the pre carry three ok with 6
times 5 is 30 i have to pre carry 3 so 1
times 5 is 5 plus 3
ok is going to be
I
or I'll take that one off 6 times 5 is
30 already pre carry the three so that 0
and then 1 times 5 i'm not gonna have to
pre carry anything
so with that I can put down to zero from
the 30 like I've already pre carry the
three that one done one times five is
five and then i'll look for the next 13
times 5 is if you don't have to pre
carry you guessed that one
ok because 35 to 50 on it pretty carry
the one of the 50 so 5 plus 1 is six ok
and then what I do is I put in that last
bit which was that five and you go with
that did you get that inside did you get
100 9065 hopefully you'll be auto
actually are start seeing how to do this
it's all a matter of working at the pre
carry
ok is it easy at the start night this
does require practice and what I'd
recommend is you would start with
smaller numbers just start off with ok
you would start with something but I
like there is something like I possibly
you know what about 423 and we're going
to times that by four
ok so that's a good one because it's a
nice straight digits not too huge for x
46 day three times for his ID
so it's less intense i can put in the 16
I can think 16 I can keep that in my
head 2 times 4 is aight 3 times 4 is 12
and have to pre carry that one so it's
gonna be a nine and a two-edged deal
with that
hopefully pretty good
anyway see here you go with it before
you start getting upset and telling you
despise this method or whatever like
that
give it a fair guy because this is
trying to reprogram your mind
and so you are you will actually about
it is mentally I can but don't expect
it's going to come to you in three
seconds flat
ok this does take a little bit of
practice sometimes this does take a
little bit of practice these sorts of
things anyway
with a bit of practice your mental math
will get faster
good luck on that anyway thanks