Abacus Lesson 19 // Subtraction-Complementary Numbers Respect to 5- TEN'S Column Video Lecture | Abacus Master Class:Become an Expert (English) - Personal Learning

all right now we are going to be doing
simple subtraction using complementary
numbers in the tens column all right so
by now you you know that you can handle
this because you did it before with
addition an addition is just the
opposite of subtraction and it's just a
reminder well let's just start with a
problem so I don't I'll talk you through
it
let's put the number 15 on our abacus 15
a 1 and a 5 is 15 and we want to take
from that number the number for 15 minus
4 well I go to take away 4 here and I
can't take away anymore because to
subtract or take away I have to move it
away from here and I can't do that and
so I have to Swit that triggers my mind
to think oh yeah complementary numbers
and the compliment to the number 4
because that's the number we want to
subtract is the number 1 so in
subtraction I added the compliment so
that means I slide that up and then move
that out of the way 15 minus 4 is 11 a 1
and a 1 11 15 minus 4 is 11 so let's do
that let's do a different problem is
just as easy as that
we it's not any harder than we did
before in the previous lesson but you're
going to now we're using the tens column
so put the number 25 on your abacus
there is number 25 on our abacus and we
are going to take from that the number
225 minus 2 well 2 is in the ones column
and we don't have
we can't take away two because they're
all already gone well how do I do that
oh yeah there's my trigger to think
complementary numbers so the complement
of the number two is the number three so
25 minus 2 well okay that means I add
three of that of way 25 minus 2 is a 2
and a 3 23 25 minus 2 is 23 so piece of
cake
if you handled if you did the problems
in the last lesson those two will have
been extremely easy so let's do
something a little more tricky let's see
if I can trick you here put the number
45 on your abacus the 4 and a 5 45 and
we are going to take from that 11 45
minus 11 is a 1 and a 1 so we're going
to start over here as we work left to
right left to right remember that so 11
well this one's easy we don't even have
to use complementary numbers we just
take that away so we just subtracted one
from the tens column and now we guys
subtract one from the ones column and I
can't everything is already down at the
bottom I a trigger for my complimentary
numbers so here we go so that complement
to the number one is the number 4 so
that means I add the complement and get
that out of the way and subtract a 5
there so 45 minus 11 is what's this
number a 3 and a 4 34 45 minus 11 is 34
so that one was kind of fun because we
have in the tens column we just did our
normal subtraction and in in the ones
column we did our complementary
subtraction let's do another one like
that those ones are fun that really
makes my brain work 88 minus 44 so let's
put the number
eighty-eight on them sound effects are
allowed with the abacus eighty-eight but
not required you don't have to make
sound effects I just makes it more fun
hey okay eighty-eight - forty-four
here's an eight and an eight eighty
eight and we are going to subtract from
the number eighty eight forty four so 88
minus forty four so we go here oh I
can't take four away here because
there's only three that I can take away
all trigger complimentary numbers there
we go okay so the complement to the
number four is the number one that means
I add one take that away and the same
thing here I can't take there's no room
for me to take away four there's only
three so oh I add the complement then
get the five out of the way
add the complement of that so 88 minus
forty four is well we're left with a 4
and a 4 44 88 minus 44 is 44 all right
here we go clear that 37 minus 33 so
let's put the number 37 on here 37 a
three and a 737 is 37 and we are going
to take from that the number 33 so we
start here 33 is written a 3 and a 3 so
can we take away a three in this comb
yes we can there's three beads with that
we can move out of the way can we take
away three in this column not without oh
there's my trigger for complimentary
numbers because I can't move three beads
down so the complement to the number
three is the number two so I add two and
get that out of the way and what are we
left with
it is the number four so there we have
it 37 minus 33 is 4 all right go print
off your worksheet and try that out see
see if you can do that it should be a
piece of cake because you're getting
this by now you've already done it with
addition and you know this is just the
opposite we're using complementary
numbers
you