Singapore Math: Grade 3a Unit 1 (part 2) Video Lecture | Mathematics Lesson for Grade 3 (Singapore) - Personal Learning

let's say I've spent the last week
collecting marbles and I have I have
outdone myself I have several huge bags
of marbles and I need to put them into
cans to essentially figure out how many
marbles I have so let's let's start
doing it and then we'll we'll try to see
based on looking at the cans how many
marbles we have so let's say I just
start you know I know that I have
thousands or you know more than a
thousand marbles so I start filling out
a thousand can so what color was our
thousand can it was green it's not
always gonna be green but in the
examples I'm doing our thousand cans are
green so let's say I have a thousand can
a thousand can here and I start pouring
the marbles in and it fills up it fills
up completely all the way I filled it
all the way up and I still have a lot of
marbles left in my collection bag so I
said well I'm probably going to need
another another thousand can so let me
get that other thousand can out so I
have another thousand can here right
here that's my other thousand can and I
start filling that one up and I fill it
up and that one also fills up all the
way to the rim so even you can even say
well how many how many marbles have I
put into can't so far well this is a
thousand this is a thousand so so far
I've filled up two thousand two thousand
marbles
mm I've already outdone what I did in
the previous example by a lot you can
think about by how much alright so let
me let me write that down so this is one
thousand can and this is another
thousand can one thousand here now let's
say that I look in my bag and I even
start to fill up another thousand can
but it doesn't it doesn't fill up all
the way so I'm like well that thousand
cans aren't useful anymore because it
doesn't help me count how many marbles
are in the can so I'm done thousand cans
I now have to fill up the next smaller
cans eyes and that's of course 100 cans
but before we go there how many total
thousand cans have we filled up well one
thousand and another thousand so we have
filled up
mm marbles into these two cans right
1000 plus 1000 mm right
or another way to write it mm so now you
know because I can tell that I can't
fill up another thousand can I take out
my hundred cans let's say I have one
year
that's one of my hundred cans and it
also fills up with marbles so I
definitely have more than a hundred
spare after the two thousand so I have
more than 2,100 marbles you could say I
take out another hundred can take out
another hundred can that one fills up as
well dum de dum de dum and you know
these marbles are super small at this
you know in this level there now
Enfield's up and I take another one
they're filling up quickly I've I've
collected many many many marbles so
there's that's a ton of marbles in there
not a ton there's exactly 100 or I
shouldn't say a ton I'll be honest
almost 100 is it done anyway
and then that's and then I take it
another can and that one fills up as
well I'm I'm I'm impressed
that fills up as well right and then I
try to fill up a 50 all right so far I
fill up I filled out 400 cans and I want
to fill out a fifth but it doesn't fill
up all the way so I'm like oh well I
can't use 100 cans anymore I have to go
to the next smallest so I still have
several you know a good number I filled
I've taken out most of the marbles out
of my original marble bag but I still
have some left and ice actually less
than 100 because I can't fill out
another 100 can so I take out the 10
cans but before I do that let's figure
out how many hundred cans we have well
this is 100 I can just write out the
number now right that's 100 that's 100
can that's 100 that's 100 and that's 100
or you say that's 100 can that's 100 can
but this hundred that's the number of
marbles I have right so this is going to
be a total of how many marbles how many
marbles are in my 400 can well you could
say I have four cans of 100 or 100 times
four well any way you look at it you
have 400 cans four times hundred
and just as a reminder you know I mean
we did the place notation when we add it
all up but this is we're still using the
place notation right when you put the
four in this place that's two to the
left that tells you how many hundred
cans you are when you go three to the
left one two three that tells you how
many thousand cans you have and so as I
said we don't have we have less than a
hundred marbles left so we go to the ten
cans we go to the ten cans and let's say
so I fill out one these are relatively
small now right because I fill out one
of them and I fill out another one of
them let me draw them ahead of time and
actually fill out two more fill out that
one fill out that one and then I try to
fill out a fourth Ken kam but doesn't
fill up I have it's something so I'm
almost I've almost emptied out my
original bag I just have a couple of
marbles left and doesn't even fill up a
ten can and I actually just pour them
out and I see that I have I don't know I
have six marbles left and they're gonna
be small one two three four five five
six marbles left
I have six marbles left so anyway we
haven't we haven't counted the ten can
so how many do we have this is one ten
can call it as one ten that's a 1/10 can
that's a 1/10 can
that's a 1/10 can or we could call this
10 marbles 10 marbles 10 marbles so
there's a couple of ways we could look
at it we could say well we have 3 10
cans or 3 tens or we could say we have
10 plus 10 plus 10 is equal to 30
marbles and so we have a total of if we
just look at those 3 10 cans that are
fold of marl of marbles we have 30
marbles and then we have the leftover
right we didn't have to put these in any
cans because we don't have a cans
smaller than 2/10 can so we just leave
these these marbles loose and we can
just count them directly doesn't take
not too hard to count six marbles and so
we just have six marbles here so my
question to you is you know we did this
I'm organizing one so that I don't slip
on
marbles but also sir I can easily count
my marbles and you can imagine it's much
easier to pour a thousand marbles into a
can until it fills than to just count
you know from one to a thousand so this
is helping me count my marbles so how
many total marbles do I have well I have
two thousand cans of marbles so that is
two thousand marbles and then I have
four hundred cans of marbles so that is
four hundred marbles and this is and
then I have three ten cans this isn't a
thirty-six I know my handwriting isn't
perfect that's that's a zero so I have
thirty marbles from the ten cans three
cans of ten that's thirty marbles and
then I have six left over I have six
left over and then we're gonna add them
all up let me add and make make my
addition sign a neutral color I'm going
to add them up and we get I mean do we
use my neutral color again maybe I'll
use blue and we get what do we say
what's a short way of writing 2,000 plus
400 plus 30 plus six
well we said you know this this place
that's three to the right of this first
of the rightmost place that tells us how
many thousand marbles we have right so
we have two thousand marbles and that's
of course what are all the places so
that's the thousands place then we're
gonna have the hundreds place we're
gonna have the tens place and then we're
going to have the ones place right so we
went one two three three to the left
that's the thousands and that tells us
we have two thousand cans we have four
hundred cans right that four that's
where we got the four from or this 4
here that - we got it from two thousands
and then this place right here tells us
how many 10 cans we have well we have
three ten cans and that's where that I
got this that three is that three or
this three and then this the rightmost
base before we learn about decimals this
writes most space is tells us how many
extra marbles did we have that didn't
fit into a 10100 you know didn't fill up
any of the can
we have six left over we have six left
over and that's Dana that's just and
that's the ones place
that's kind of good to call them the
free marbles and the way we would read
this is 2436 marbles and that's not too
difficult we could have almost read it
before adding them together we could
said 2436 marbles so either way you look
at it it's hopefully not not too
difficult so actually let's let's let's
just do some practice actually reading
numbers so I'm going to write number
down and then I want you to maybe you
want to pause it and read it before I
write it so I'm gonna write it in a
neutral color so I don't give you all
these cues so let's I'm just gonna write
this number down this is this is a
different example from what I was doing
so let's say this is the number I have
to resist the temptation to say it as I
write it and so you might want to pause
and and say it yourself or try to say it
because I'm about to do it well how do
we think about this well as we said
let's let's write it in terms of kind of
the number of cans we have and maybe the
colors will help this eight this eight
number what does that tell us that tells
us how many free marbles we have in this
example so we have eight free marbles if
we go one place to the left we go to the
tens place right this is the tens place
this is let me make sure I'm using the
tens color the appropriate color for
tens so this is tens tens I don't know
if you can read that that's tens this
one those ones ones or free marbles but
in the tens place that tells us how many
ten cans we have or how many groups of
ten well we have nine groups of ten
right and or another way it's 90 but let
me just write that there color code it
if we go one more space that tells us
how many cans of 100 we have I'll just
write H 400 because I'm running out of
space that tells us how many hundred
cans we have and then this this this if
we go a further space to the left that
tells us how many thousand cans we have
I'll just write T 4,000 right and if we
wanted to do it
in the previous problem in Reverse we
could actually write this as five
thousand five thousand plus 900 plus
nine hundred plus 90 right this is nine
tens nine times ten is 90 plus 90 and
this is just eight eight I'm gonna do a
neutral color to add them up this equals
that so how do we say it well it's five
thousand five thousand nine hundred nine
hundred ninety-eight five thousand nine
hundred ninety eight five nine nine
eight is or five nine nine eight is read
as five thousand nine hundred ninety
eight so almost when you read it out
you're essentially just telling people
five thousand or five thousand cans nine
hundred or nine hundred cans ninety or
nine ten cans at eight we eight cans
that didn't fill up you know a ten can
and so some way let's do one more let's
do one more I try to keep my videos
under ten minutes but you know when I
get excited I just keep going let's do
one more and I have to be silent so they
mistakenly so here's the number I want
you to say it pause the video and try to
say it and maybe you want to you know
expand it out mate draw it cans do
whatever you need to do this is good
practice so I'm gonna do a shortcut well
I hopefully pause now try it and I
assume you've just paused it so i will
restart it so let's let's start here
what was well it's good to start from
the left actor because when you read it
you read from the left and you start
with the biggest number of cans first so
this was what if you go this this you
know two spaces to the right one two
three spaces to the left of this first
one well this was what this was a
thousand spit place right this was
thousands thousands so what is that
that's six thousand six thousand and
then what is the next place over to the
right well that's the hundreds place
right and you could remember that
thousand divided by 10 is 100 there's
different ways to think about it so
that's hundreds so we have zero hundreds
interesting
we couldn't feel after he filled out a
6000 cans we couldn't even fill out a
hundred can and so we had a few left
over we go one more space to the right
that's a 1 and that tells us the number
of 10 cans we have not tin cans 10 cans
so we have one 10 can and then this last
space what is that that tells us the
number that just free marbles right
liberated marbles so that's just 2 2 or
2 right so that's 2 so you could write
this if one went to 6000 you could say
6000 0 110 - but obviously you've
probably never heard someone's talk like
that and and actually you don't even if
there's zero a certain place you don't
even mention it so the way you say this
is you say there's this is six thousand
six thousand you don't say zero hundred
you just say six thousand and then you
don't say ten - what is 10 plus - well
10 plus 2 is 12 right so you say this is
six thousand and twelve marbles but if
you were to expand it out it would be
six thousand it would be let me write
that down
six thousand plus plus ten plus two and
obviously the hundreds I could write the
zero hundreds there right zero times 100
zero times 100 maybe that would be three
zero zero - and I shouldn't confuse you
like that so six thousand plus zero
hundreds plus ten plus two you could say
six thousand ten - that doesn't sound
good so people say six thousand twelve
and so that might be a little less
intuitive but hopefully you get the
sense for it I will see you in the next
video