Singapore Math: Grade 3a; Unit 1 (part 6) Video Lecture | Mathematics Lesson for Grade 3 (Singapore) - Personal Learning

let's see if we can take everything
we've learned about place value and do
some more number comparisons so what
would what would you say if I asked you
which is smaller so I want to know which
is smaller this number and I'm not
saying it because it might give you
clues and I encourage you to say it
yourself
this number or this or this number which
is smaller well let's let's draw it out
and see if we can get it to get a sense
of it or maybe you remember what I told
you in the last video so if first of all
let's let's look at the ones place
I'll start kind of in the non-intuitive
way so here we have two ones and I could
draw um this is you know two marbles two
marbles here here we have five marbles
in the one it's place 2 3 4 5 in the
tens place here we have two cans of 10
marbles going back to our original
analogy so this is one can of 10 that's
another can of 10 I'll draw the marbles
in in a second here we have 5 1 2 3 I'm
trying to draw it to scale now just to
give you more intuition 4 5 and let me
fill them up with marbles so there's
marbles and all of these all right 10 20
30 40 50 and here you have 10 20 and
then in both cases in the hundreds place
we have the number 3 the digit 3 and
that tells us we have three canisters of
a hundred you could kind of or 300
marbles and so those those are much
bigger those are like you know each of
those canisters are going to be ten
times the size of that so it's gonna be
like that like that probably even bigger
but I don't have space to draw out that
big dad like that and like that and I
could draw in the marbles but you know
just see you at the point filled with
marbles filled with marbles
so just so you realize so this is 300 so
they have three cans of 100 or 300 this
also is 300 here you have five cans of
ten or fifty here you have two cans of
ten or twenty let me draw a dividing
line and make sure we don't get the two
numbers confused and here we have two
ones or just two and here your five ones
are just five so this 300 plus 50 plus
two this is 300 plus 20 plus five now in
the last video I said you know you
should just focus on the largest place
in this case it was 100 it was hundreds
place but when we compare them we have
three huge canisters here 300 marbles
but we also have three huge canisters
here so it actually has the same number
of hundreds so when we when if those are
equal then let you gotta move on to the
next largest place so now we look at the
the buckets of ten well here we have
five buckets of ten and here we have two
buckets of ten so clearly we have more
buckets with the same number of hundreds
but we have a lot more buckets of ten
here than we have here so this number is
the 352 or 352 is a larger number than
325 or we could say that 325 is the
smaller number and if you just take the
threes away you know that fifty-two is
larger than 25 and how do you know that
because the largest place value the five
that represents 50 the value of 50 well
this two represents a value of 20 right
and they both have 300 added to this but
those are equal let's do let's do more
interesting problems so I'm going to
write two numbers so let me just say I
have I have this then is blank so the
digits here seven zero three one is
blank then
seven three zero one and I want you to
say either greater than or I want to say
greater or less well let's let's do what
we did before and I don't think I have
to draw the buckets this time you go to
the largest place value and this is ones
tens hundreds thousands ones tens
hundreds thousand so in the thousands
place we have seven thousand here that's
seven thousand well we also have seven
thousand here so the thousands place
they're equal so let's go to the next
largest place in the hundreds place we
have zero hundred while here we have
three hundreds so we immediately know we
actually don't even have to look at the
rest of the numbers we really know that
you know since in the largest place
value they were equal but in the next
largest the hundred space three hundred
is a lot more than zero hundred so we
immediately know that this number is a
larger number than this and that makes
sense seven thousand three hundred and
something is larger than seven thousand
thirty one because three hundred and one
is larger than thirty one so seven
thirty one is less then seven thousand
three hundred and one let's do another
one
they had this number eight zero zero
four is blank that should be a ban like
that not Bend blank then eight zero four
zero just like we did last time the
thousands place we have eight thousand
we have eight thousand here we have zero
hundred zero hundred we have zero ten
let me do that well I did that in the
hundreds color where you get it and then
we have four four ones which is this 4
here we also have zero hundred zero
hundred but in the tens place what do we
have we actually have four tens
for tens so what do you say you say well
you go to the largest they both have
eight thousands they both have zero
hundreds but in the tenths place this
number has more tens so it doesn't
matter what happens in the ones place
because the tens is a bigger is a larger
place so this is once again the number
on the right is a larger number so we
would write less 8004 is less than eight
thousand and forty or you could say well
four is definitely less than forty so
eight thousand four is less than eight
thousand and forty let's do one more
like this I'll switch colors arbitrarily
so three seven five six is blank then
three five seven six is interesting
because these two numbers they're just
we just switched the seven and five so
which ones bigger just like we did the
last few times look at the thousands
place that's three thousand that's three
thousand they're equal in a thousands
place then let's go to the hundreds
place seven hundred versus what five
hundred well seven hundred is definitely
greater than five hundred so this whole
number it doesn't even matter what's
over here this number is greater than
this number and this is three thousand
seven hundred fifty six
this is three thousand five hundred
seventy-six and you think about rough
terms three thousand seven hundred is
larger than 3500 with that I think
that's enough of that type of problem
let's let's do a even another twist on
it let's say I gave you three numbers
I don't want to read out the numbers
just cuz they may give you a clue so
what I want to know is what is the
largest or what which of these three
numbers is the greatest well once again
you go to the largest place value and
all of these are four-digit numbers is
ones tens hundreds thousand let's go to
the thousands place so this is five
thousand right that five represents five
thousand special experience
four thousand this four this four
represents four thousand so this number
here has the most thousands so this is
going to be the largest number so this
is the luck
winner for largest so what's the
smallest number well these have the same
in the thousands place in the hundreds
place that's nine hundred that's also
nine hundred and they get different in
the tens place this is 80 well this is
70 so this is larger than this eighty is
larger than 70 so this is the smallest
number because it's definitely smaller
than this one and it's smaller this was
well so this is the smallest smallest
let me let me ask you some thinking
questions what is the smallest
three-digit number well one way to think
about is what is the largest two-digit
number you know the two digits you know
the you go one and you go you keep
adding and you go to 9 and then what's
after nine you go to 10 10 is the first
two digit number so that's the smallest
two digit number and then you keep
counting you go 11 12 you know you keep
going you go 20 this means just you keep
going 20 30 40 50 you know there's
numbers in between right 60 70 80 90 and
then go 91 92 93 94 95 96 97 97 98 we're
still doing two-digit numbers all of
these are two-digit numbers but what's
the number after 99 as we said you add
one more so then you have another 10
but then you'd have ten tens so you
actually have a hundred so the first
three digit number is a hundred and so
far and so so that is the smallest three
digit number so what's the largest three
digit number well we're gonna keep
adding we're gonna keep adding until we
have to go so what's the first what's
the first four digit number the first
four digit number is this the smallest
four digit number is 1,000 right so the
largest three digit number is going to
be it has to be one smaller than the
smallest four digit number are probably
confusing so what's one less than this
you might have guessed the pattern right
one less than 100 is 99 or 99 plus one
is 100 so if you go one less than a
thousand you're at 999 so this is the
largest the largest three-digit number
and so you know I would encourage you to
think about what happens when you add
one here you not only get another ten
but then you have ten tens so then you
actually have another hundred and then
you have ten hundredths so then you have
a thousand let's do a couple more let's
just let's just keep going what is the
smallest why should I already figured it
out what is the smallest I'm looking at
this this the Singapore math book it
says what is the smallest four digit
number already told you it's 1,000
that's the first fortunate number and
you can think of the pattern what is the
greatest four digit number well the
greatest four digit number is the number
where I have where I have the highest
digit in every place so what's the
highest digit that I can put in every
place well nine right so I put a nine a
nine a nine and a nine in general if I
say what's the largest three-digit
number well I have to put the largest
digit in each place so it's nine nine
nine just like we figured out before now
let's let's do some number ordering so
let's say we had these numbers and I
wanted to order them
3412 3142 3142 4123 2431 and i want to
start with the largest of these numbers
so which is the largest let's look at
the largest place value three thousand
three thousand four thousand two
thousand so this is the largest right
because it's got four thousands so 4123
is the largest cross it out what's the
next largest well I can already tell you
what the smallest is right three
thousand three thousand two thousand
this is the smallest we could put that
there
two thousand four hundred and thirty one
and so we have to figure out what's the
largest between these two well this is
three thousand four hundred right three
thousand four hundred while this is
three thousand one hundred so this is
bigger than this right four hundred
Trump's one hundred so this is three
thousand four hundred and twelve and
then 3142 and that's our order from
largest to smallest what if I gave you
these numbers say 1892 nine thousand and
three and I encourage you to pause the
video try it yourself and then check
your answer with what I did maybe you
can find careless mistakes that I made
so what's the largest but well this
order these from smallest to largest so
this we did from largest to smallest
let's go the other way let's go from
smallest to largest so what's the
smallest of these numbers so you might
be tempted to you know say well we have
one thousand nine thousand eleven
thousand scholars 1,009 1,010 nine
thousand but look carefully this isn't a
nine thousand what's the place here this
is the hundreds place this is nine
hundred this this number actually
doesn't even have a thousands place
right the thousands place would be here
where there's a blank here you can even
put a zero before the number there so
actually you know this has 1,000 this
has nine thousand this has one
this has zero thousands so this is the
smallest number right here it only has
three digits so the smallest number is
913 you can scratch that out what's the
next smallest well we have one thousand
nine thousand one that we dis is the
biggest right nine thousand so we could
put that here nine thousand and three
and so this is 1800 this is 1700 so 700
is smaller than 800 so this is the next
smallest after 913 1703 and then you
have 1892 and then of course nine
thousand and three I think that's good
for now I will see you in the next video
I don't want to make these too long see
you soon