Multiply and Divide Integers - Mathematics, Class 7 Video Lecture

hello welcome to master math my name's
Stan Lyle and today we're going to talk
about multiplying and dividing integers
during the lesson you'll come across
some you try it pages when you get to
one hit the pause button do the problem
and then hit the forward button to move
on to the answer math is easy you will
do well math is easy you will do well
III I hope that work I paid a lot of
money to buy from special CIA agents a
hypnotic slide that will hypnotize you
and allow me to convince you of anything
I want and I've now convinced you that
math is easy and you will do well
learning to multiply and divide integers
I'm going to assume you guys know how to
multiply and you guys know how to divide
but I bet a lot of you get a little
confused determining what the sign of
the outcome is going to be in a
multiplication product problem or a
division problem and it can be a little
confusing those are the factors of the
problem we're dividing six by minus two
and six as a sign it's positive if
there's no sign shown and then we
assumed it to be positive and two has a
sign it's minus 2 that's 6 divided by
minus 2 well if I divide a positive
number like 6 by a negative number my
minus 2 is my aunts are going to be
positive or negative the factors in this
multiplication problem are minus 11 and
minus 2 I've got a minus number times a
minus number
well my results be negative or positive
well there's some easy rules you can
remember to help you figure this out if
the signs of both the numbers you're
working with are positive then your
answer will be positive
if the signs of both of the numbers
you're working with they're negative
then your answer will also be positive
if the sign of both of the numbers
you're working with are different one is
positive and one is negative then the
answer is going to be negative if both
of the numbers you're either multiplying
or dividing by are positive the answer
is going to be positive if they're both
negative the answer is also positive so
if the sign of the two numbers you're
working with in a multiplication or a
division problem are the same they're
both positive or they're both negative
then the answer is going to be positive
but if they're different if the signs of
the two numbers you're working with are
different once positive the others
negative then the answer is going to be
negative positive six times positive
seven gives us a positive 42 result
negative six times negative seven also
gives us a positive result but if one of
the signs is different in the
multiplication or the division problem
then you're going to get a negative
answer well what happens if I've got
more than two numbers in this problem
for instance in this example I've got
minus 6 times 5 divided by minus 2 well
my answer be positive or negative well
that's kind of easy all you have to do
is do one problem or one part of the
problem at a time
for instance in -6 times 5 divided by
minus 2 let's do that part first minus 6
times 5 minus 6 times 5 equals minus 30
I've got one negative and one positive
so my answer is going to be negative now
my problem is minus 30 divided by minus
2 the mine
- I haven't changed I got a negative
number divided by a negative number
negative divided by negative is going to
give me a positive answer 50 excuse me
30 divided by 2 is 15 now you try it - 6
times 6 hit the pause button do the
problem on a piece of paper and then hit
the forward button to see the answer
I've got a negative number times a
positive number so I've got one of each
signs my answer is going to be negative
6 times 6 is 36 so minus 6 times 6 is
minus 36 try this one
you
just like in the last problem I've got a
positive number and a negative number
that I'm working with and if one's
positive and ones negative the results
are going to be negative 35 divided by
minus 7 is minus 5
you
well in this one both of the numbers
were working with are negative so if I
got two negative numbers or both the
signs are the same then my answer is
going to be positive minus 10 times
minus 6 equals 60 the number of moose in
North Country Park near Minneapolis has
been decreasing over the past five years
the table shows the estimated number of
moose what was the mean annual change in
moose population if you forget mean
means average to average you sum up the
changes and divide by the number of
changes to get the mean
you
well the changes of moose population
we're -20 between the first year in the
second year and then they lost 45 moose
and then they gained 10 moose and then
they lost 35 more moose so we have to
add those up minus 20 plus minus 45 plus
10 plus minus 35 and that totals up to
minus 90 now we've got minus 90 divided
by the number of units that we added up
1 2 3 4 so minus 90 divided by 4 is 22
and 1/2 evaluate the expression x times
2y divided by Z where x equals 6 y
equals minus 5 and Z equals minus 2
okay well they tell us that X equals 6 y
equals -5 and Z equals -2 so we have to
substitute into the equation x times 2y
divided by Z we have to substitute into
that equation 6 where X was and where Y
was we have to substitute -5 and where Z
is we have to substitute minus 2 so the
equation becomes 6 times 2 times minus 5
divided by minus 2 6 I solve that part
of the expression 2 times minus 5 I got
a positive number and a negative number
my answer is going to be negative 6
times minus 10 divided by minus 2 now
I'm going to do the first part of this
equation 6 times minus 10 and that's
minus 60 my minus 2 comes down in
exactly the same format now I've got
minus 60 divided by minus 2 that's a
minus divided by a minus I'm going to
get a positive answer positive 30 well
that's our lesson on multiplying and
dividing integers and I hope you found
it helpful now it's time to test your
skills go to wwm astra f info find the
tab for worksheets under 7th grade first
quarter you'll find a worksheet entitled
multiplying and dividing integers
download it print it and try it on your
own and come back to master math dot
info real soon