Abacus Lesson 25 // Subtraction-Complementary Numbers Respect to 10- ONE'S Column Video Lecture | Abacus Master Class:Become an Expert (English) - Personal Learning

less than 25 learning the abacus
subtraction using complementary numbers
with respect to the number 10 in the
ones column all right so here we go now
this is this is a lot of fun and I think
you're going to enjoy this more than the
addition because it's different and it
gets you to think now just to point out
even though we're using the ones column
and in the past we've only always used
the ones column at this point but since
we're doing these numbers these problems
with respect to the number 10 we're
going to have be using a little bit
because we're doing subtraction so the
first problem that we're going to do is
10 minus 7 so we're going to start with
the number 10 on our abacus and we are
going to subtract from that the number 7
well the 7 is in the ones column we
don't have enough beads there to take
that away from it so remember you we've
done this exactly the same as we've done
before when we're using complements and
we're subtracting we're going to add the
complement all right so here we go we're
doing subtraction the compliment to the
number 7 is the number did you say it
out loud can you get it did I it's 3 the
compliment to the number 7 is 3 so
here's what we do is we add 3 slide 3
towards the beam and we're going to take
that one away in the tens column so 10
minus 7 is 3 I can see that that works
yeah we can do this
let's do another one kind of similar to
that let's do is 10 minus 6 and in your
head I know you can probably do this but
it'll we're learning abacus brain so
here we go 10 minus 6
this says ten and one is zero and we
don't have six beads to take away from
here there would have to be a number
bigger than 6
in this ones column to do that but
there's a zero so what do we do we add
the compliment the compliment to the
number six is four all right that means
we slide four up and take away this bead
in the tens column so 10 minus 6 is 4
all right I can see the wheels starting
to turn here we go let's do one just a
tad bit no it's not any harder which is
different
let's do 11 minus 8 11 is a 1 and a 1
that's how you write the number 11 1 and
1 and we're going to subtract from that
the number 8 11 minus 8 so here we are
in the ones column and we don't have
enough beads there we only have one so
we've got to use complementary numbers
and the compliment to the number 8 is 2
that means we add 2 so I added 2 to the
ones column and I'm going to subtract
this bead in the tens column so 11 minus
8 is 3 all right here we go the next one
12 minus 9 there's the number 12 on our
abacus and we're going to subtract from
that the number 9 not enough beads that
means we add the compliment the
compliment to the number 9 is 1 and we
take away that right there 12 minus 9 is
what do we have left 3 now I know you're
getting this is probably a piece of cake
let's just do like 2 more and I think
you'll have it let's do 17 minus 9
let's try that one and a 7 17 minus 9
well nines are easy
subtraction because all we have to do is
add that one there and take that one
away there 17 minus 9 is 8 piece of cake
oh that's fun all right one last one and
I think you'll have this subtraction
using complementary numbers in the tens
column
let's do 12 minus 8 all right so let's
put the number 12 on here 12 minus 8 we
don't have enough we know we need to new
use complementary numbers the complement
to the number 8 is 2 and we're
subtracting so that means we add the
complement and then take away that beat
in the tens column 12 minus 8 is 4 now I
know you're getting this and that was
probably a piece of cake for you and I
know you'll get this so let's let's go
print off that worksheet and just work
through the problem fly through because
you probably will and it's it's fun the
next one's going to be even more fun the
tens column
you