Singapore Math: Grade 3a Unit 2 (part 11) Video Lecture | Mathematics Lesson for Grade 3 (Singapore) - Personal Learning

let's do some word problems as you can
see my handwriting has improved
dramatically I've been practicing no I
actually just figured out that I could
actually type on this thing anyway so
what is this word problem say Jamie
picked 17 flowers and Lindsay picked 12
they gave away 20 of the flowers how
many flowers were left let's think about
this
Jamie picked 17 flowers let me draw that
so Jamie picked 17 flowers so let me
draw something that represents the 17
flowers at Jamie picked this is kind of
my traditional Singapore bar in yellow
and the length of this is going to be 17
and the units are flowers 17 flowers and
what does it say it says Lindsay picked
12 and so this just thing that they're
saying well you know one person pick
some flowers another person picked more
then they gave away 20 of the flowers so
it sounds like they saying you know they
combined their flowers gave 20 and how
many were left so what we want to do is
we want to combine the flowers at Jamie
and Lindsey picked so Lindsey picked
twelve flowers so Lindsey's flowers so
we're gonna combine them Lindsey picked
twelve just Lindsey's flowers right
there she picked 12 and so well first of
all how many total hours did they pick
well twelve plus seventeen that's 29
dead in a neutral color so the total
flowers victor is 29 right 17 plus 12 2
plus 7 is 9 2 29 and they say they gave
away 20 of the flower so they gave away
20 of the FAR's what color do I want to
do that in I'll do that in blue and
green no no I used green I'll do it in
brown so they gave away 20 of the
flowers they gave away 20 of the flowers
how many flowers were left so they gave
away 20 so we could view that's their
total and if they're they gave away 20
let's say that this is
what they gave away that's the I
walk that I didn't want to do it like
that oh no I didn't want to do that
especially I didn't want to lose the
window no boy everything's
self-destructing now there you go okay
let me draw it with the traditional way
so say they gave away 20 of the flower
so it's gonna be something like that
that's how much they gave away 20 and
I'm overriding 29 all right so how much
did they have left so that they had 29
the whole length of this thing's 29 they
gave away 20 of them so the amount that
they're gonna have left is this right or
the difference between 29 and 20 all
right this distance right here is 20 so
it's 29 minus 20 well that's 9 so they
have 9 flowers left let's do the next
problem and now we're on page 37 of the
book let's see how well versed i am in
typing let's see if i can pull this off
that's like my typing window and i win
it it says a hundred and twenty-five
children took part in a mathematics
competition 54 of them or girl not
grills girls
how many more boys than girls were there
were there there you go how many boys
more boys and girls were there so let's
see if we can handle this one 125
children took part in a mathematics so
that that tells us the total that's the
boys plus the girls is 125 all right 125
54 of them were girls so how many boys
were in the competition so if we if we
do boys and girls and I'll use
stereotypical colors because
any better so this is the number of
girls so that's the number of girls
which we don't know oh no we do know
that's 54 there are 54 girls 54 girls
that's given here 54 of them were girls
and then we have some number of boys
which is unclear draw that so we have
some number of boys which we don't know
boys but what we do know is that the
boys and the girls combined are 125 so
we know for example that this entire
number is 125 the boys plus the girls
are 125 so how many boys are there
what's essentially going to be the
difference between 125 and the number of
girls so boys is going to be equal to
125 minus the number of girls and we get
to minus the girls right
and think about this actually this is
kind of a little bit of pre-algebra
this statement actually comes directly
from the fact that boys plus girls is
equal to 125 right this is called an
equation an equation just says well what
I have on the left side is equal to what
I have on the right side and then
essentially if boys plus girls is 125 if
I took the girls away from both sides of
this equation I get this right here
right if I took the girls away from this
side I get just boys on this side boys
but if whatever I do to one side of
equation have to do the other so I have
125 so I did - girls here but now stuff
to do - girls on this side and that's
where I have the 2125 - girls if that
confuses you ignore it but just think
about the fact that the boys and the
girls 125 and that's the same thing as
saying 125 minus the girls is equal to
the boys and we know that the girls are
54 so we'll say B for boys is equal to
125
- 54 and let's work that out up here in
this corner so 125 - 54 5 nights 4 is 1
well we have to just essentially 12 -
571 so the boys are 71 so are we done
well no they didn't ask us how many boys
are there they asked us how many more
boys than girls are there so they want
to know the difference between the boys
and the girls right so what's the
difference between the boys and the
girls
so it's essentially going to be the boys
- the girls equals what well we know the
boys they're 71 boys and we know that
there's 54 girls and I you could do that
in your head but if you don't want to do
that in your head let's do that in the
corner up here so 71 boys - 54 girls
let's see so let's borrow a 10 so that
becomes a 6 that becomes at 11 11 minus
4 is 7 right I always have trouble with
11 yeah i xi minus 4 is 7 6 minus 5 is 1
so there's 17 more boys than girls and
if we actually work well I won't worry
about that let's do the next video I'm
excited about my ability my newly-found
ability to type these things let me do
it in a new color let me do it in a bold
yellow make the typing box that's my
typing box now what does it say Ally
collected that's actually the name of my
cousin who figured out a new way to
subtract numbers without borrowing but
anyway Alika collected 137 stamps he
collected 27
stamps less than his sister how many
stamps did they collect all together
okay
so in order to figure out how many Ali
and his sister combined collected we
have to figure out how many did his
sister collect we know it all he
collected 137 so we have to figure out
how much his sister collected well how
do we do that well he collected 137 let
me draw that
Ali collected 137 stamps so we can make
that with a little bar like that and the
length of course is 137 that's how many
stamps all he collected and it was 27
less stamps than his sister so if I were
to draw his sister stamps you know I
would be a bit I could do it this is a
Singapore math style so it's gonna be
more right I'll he collected less than
his sister his sister collected more
stamps and how many more did she collect
well we know that he collected let me do
that in a different color so it says he
collected 27 stamps less than his sister
so the difference between the amount Ali
collected this is Ali and his sister
that these numbers clash kind of hard to
look at but anyway the difference
between Ali and his sister is 27 stamps
so this distance or this difference is
27 stamps so how many stamps also how
many steps is a sister collect well
think of it this way the difference
between Ali's sister stamps and his is
27 or you could say Ali stamps plus 27
is equal to the sister stamps so how
many does his sister collect so this
this length right here is going to be
137 plus 27
what is that 7 plus 7 is 14
but before here in the ones place and
then we could take carry the 1 or just
write the 10
it's four plus tents put the ten there
one plus three is four actually this is
10 plus 30 is 40 plus 20 is 60 and then
yet bring down the hundred so she
collected 164 stamps fair enough now
they want us to know how many stamps did
they collect altogether and I'm picking
my color how many and that's that's too
similar to a color I've already used I
use this one how many stamps did they
collect all together so essentially they
want to know how many total stamps the
ally plus his sister how many stamps did
they collect well Ally collected 137 the
sister we just calculated collected 164
stamps so we just have to add these two
numbers and that's the total number of
stamps and you could almost view it as
you've took this bar and you put it
beside this and measured that total
length but anyway what's 7 plus 4 it's
11 put the 1 in the ones place put the
10 or the tens digit in the tens place
10 plus 30 plus 60 is a hundred that's 0
tens and 100 or you could say that 1
plus 3 plus 6 is 10 carry the 1
either way 100 plus 100 plus 100 is 300
so all together they collected 301
stamps I will see you in the next video