Singapore Math: Grade 3a Unit 2 (part 4) Video Lecture | Mathematics Lesson for Grade 3 (Singapore) - Personal Learning

let's do some more word problems so
we're on page 21 I think this was still
unit 2 so 134 girls 134 girls and 119
boys 119 boys took part in an art
competition took part in an art
competition art competition competition
competition how many more girls and boys
were there how many more girls then boys
were there so let's see if we could draw
this out using the standard Singapore
Math bars or whatever they like to call
them so let's say they were 134 girls
134 girls let's draw a bar representing
the hundred and thirty-four girls here
the unit of length is girls as opposed
to balloons or cookies so that's 134 and
then there were 119 boys
so let's I'm using stereotypical colors
for boys and girls let's see probably
don't know what stereotypical means you
can ask someone at 119 boys 119 is a
little shorter than that so I'm just
getting a rough sense of things so let's
say that this is the boys right here
that's the boys and they're the unit is
boys maybe the unit for both is people
or kids that's 119 boys and then we
don't care what they took part in but it
happened to be an art competition so it
says how many more girls and boys were
there so how many more how many let me
do this in it how many more girls than
boys were there if we have 134 girls in
hundred nineteen boys is essentially
asking how many
more girls are there than boys so how
many more was going to be this distance
right here right because this is going
to be the difference between the girls
and the boys or essentially how many
more girls there are there than boys and
then how do we figure out the difference
between two numbers we subtract the
smaller from the larger so we have 134
pick a neutral color we have 134 minus
119 and let's see if we've learned how
to regroup or borrow whatever you want
to call it properly so let's see this
one is larger than that well it's equal
to that one so that's fine we could
subtract the hundreds place we have 30
here and 10 here we could subtract there
we have a 4 in the ones place and a 9
there so that doesn't work so we need to
somehow take some numbers from what is
from this area and add it to this 4 so
the easiest thing to do is to take a 10
alright so we have three tens let's take
one away so we have two tens and so we
took a 10 away and when we put a 10 in
the ones place that becomes a 10 so
what's 10 plus 4 what's 14 right just so
remember we took a 10 we added the 10 to
the 4 14 and so when you take a 10 this
was 30 so it becomes 22 2 in the tens
place is the same thing as 20 and now
we're ready to subtract 14 minus 9 is 5
2 minus 1 is 1 and then 1 minus 1 is 0
but we don't have to write it because 0
1 5 is the same thing as 1/5 so there
are 15 more girls than boys so this is
the length that is 15 or that 15 is the
difference between the number of girls
and the number of boys let's do another
one
okay mail in mail in saved 184 dollars
saved 184 dollars
she saved 63 she saved 63 dollars more
than Betty more than Betty how much did
Betty save how much did Betty save I
don't haven't sis said this recently but
enough are right down the prompt right
pause the video and try it yourself
how much did Betty not cent and save so
pause it now if you want and I will now
explain it
the Singapore Math Wayne so male in
saved 184 dollars let's see if we can
draw so this is Mei Lin saved 184
dollars so what is that statement let's
draw a Singapore Math bar this is what
Malin saved units here are dollars which
is in some ways the most interesting of
all the units so that's 184 that's what
Malin saved
she saved sixty three dollars more than
Betty interesting
she saved sixty three dollars more than
Betty so we don't know how much Betty
say let's let's let's how much Betty
saved is in yellow
how much did Betty save we don't know if
we can draw it right we know that
Betty's Abe less than male in right
because if male in save 63 more than
Betty so it's this is Betty this is the
amount that Betty saved this is Betty's
bar Betty's bar I don't know I'm just
picking a random length so this is Betty
savings
Betty's saved and this part here that
says male in the she here is May Lane
right male in save 63 dollars more than
Betty so that essentially sad tells us
that the difference between the amount
male in saved here at the
and the amount Betty saved is $63 so
this distance right here is 63 you could
do that a bunch of ways you could say if
Betty saves 63 more dollars she would
have saved the same as mail-in or you
can say if male in save 63 less dollars
you would have saved the same as Betty
but the bottom line is the difference
between the amount mail-in saved so this
is M for male in B for Betty the
difference between the amount mail-in
saved and the amount penny saved is 63
dollars or you could say the difference
between the amount mail-in saved and 63
is the amount Betty saved so how do we
figure out the amount Betty saved well
we would take essentially well think
with this yellow is essentially going to
be 100 84-63 right so what is 180 let's
write that down
I'll do it in another color in green
because we're dealing with money
184 minus 63 not 6463
since 1 is greater than nothing 8 is
greater than 6 4 is greater than 3 so we
can just subtract 4 minus 3 is 1 80
minus 60 is 20 or 8 tens minus 6 tens is
two tens and then 100 or 1 in the
hundreds place - none think it's just
one in Donner's place so 121 so Betty
saved 121 dollars and if you do the math
you can see that 184 which is what
Mahlon saved is 63 dollars more than 121
let's do one more
John red 32 pages in the morning John
red 32 pages in the morning
he read 14 pages less in the afternoon
let me that in another color he read 14
pages less I was something in the
morning in the afternoon afternoon
afternoon this has a part a and a part
be fascinating so part a asks us how
many pages did he read in the afternoon
how many pages did he read in afternoon
afternoon and Park B asks us Part B asks
us how many pages did he read all
together it's a two-part how many pages
read all together all together okay so
let's see let's do our Singapore Math
bars so John read 32 pages in the
morning so let's just draw a bar that
shows how much he read in the morning so
that's 32 32 pages that's how much she
read in the morning and we could we
could write down morning and then it
says he read 14 pages less in the
afternoon so let's say if this is the
number that he read in the afternoon
it's going to look something like this
we don't know the exact number just yet
but we'll figure it out shortly so this
is the afternoon afternoon and says he
read 14 pages less of the afternoon so
however much this is the difference
between the afternoon in the morning is
14 let me look at neutral color so this
distance right here or this size
whatever you want to say is 14 right the
difference between the morning and the
afternoon is 14 and the morning was 14
more so this is 14 we could draw a bar
here
so we could say the morning the number
of pages in the morning - 14 is equal to
the number of pages he righted the
afternoon so let's do that let's do that
first part and actually so the afternoon
so if we see he read 32 pages in the
morning and it's 14 more than he read in
the afternoon let's subtract 14 and what
do we get
well first of all I see 3 is greater
than 1 but 2 is not greater than 4 so
we're going to have to regroup or take
away take some of these 10 so we have a
2 let's take 10 from this 30 so if we
take 10 from 30 this becomes a 20 right
2 in the tens place is the same thing as
20 and then add the 10 here we get a 12
right so 12 minus 4 is 8 and 20 minus 10
or 2 minus 1 in the ones place is 10 or
one right there so he read the afternoon
he read 18 so the answer there is 18 and
then the second part of the problem asks
us how many pages did he read all
together well that's going to be the
morning plus the afternoon so what we
could do is we could take that afternoon
size and we could add it to the end
right here it has to be the exact same
length roughly I just took this and
moved it over there and so this is the
afternoon after noon all right because
they want to know all together and so
this this length right here we just
figure it out in part a of the problem
is 18 so how many pages did he read all
together well that's the sum of the
pages he read in the morning and the
pages he read in the afternoon and that
is 32 plus 18 and so what is 2 plus 8
well it's 10 right and you can't write a
10 here but what we can do is we could
say well that equals 110 and no ones so
we'll write no ones and 110 right 10 is
you know it's 110 so if we could just
instead of putting in the ones place
because it won't fit there we'll just
put it in the
hence place as just the digit one right
and one in the tens place represents ten
and then we have ten plus 30 plus 10 or
one plus three plus one in the tens
place and that equals five but since
it's in the tens place it represents
this represents 50 plus zero ones or the
whole thing is 50 so how many pages did
he read altogether he read 50 pages see
you in the next video