Download Adding and Subtracting Integers

Lesson # 32
Adding and Subtracting
Integers
Wanna be “smartless”?
If not
Pay
Attention !
We have already learned
how to…
Add and subtract
positive (+) and
negative (-)
integers…
But sometimes it is
nice…
To get a little
review.
So let us review the rules
If we are adding two
“ + ” numbers.
Then we add and we
will get another larger
“ + ” number
If we are adding
two “ - ” numbers…
Then we add the
two numbers and
the answer is a
“ - ” number
But what if we are
adding one “ + ”
and one “ - ”
number?
Well then we take the
sign of the
largest number and
subtract.
What about
subtracting…
If both numbers are “ +
”
Then +a – +b = +c
If a > b
Or
+a – +b = -c
If a < b
If both numbers
are both “ - ”…
Then -a - -b
Is the same as saying
-a + + b
So we take the sign of the
largest and subtract.
Let’s look at when
one number is “ + ”
and one is “ - ”
If the first number is “ + ” and
the second number is “ - ”
+a - -b
This is the same as +a + +b
So we simply add!
If the first is “ - ” and the
second is “ + ” then…
-a
- +b is the same as
-a + -b
so we add the numbers
and the answer is “ - ”
Lets try a few
examples…
How about -2 + -7 = ?
That would be
-9
Let’s try
-15
+
+6
=?
Well if we take the sign
of the largest and then
subtract the two
numbers that would
be…
-9
Let’s try a few subtraction
examples…
How about -8 - -2
remember that is the same
as
-8 + + 2
which is… -6
Don’t forget…
If a number
does not have a
sign in front of
it then it is a “ +
” number.
Have you got it?
Good, you got it…
Now you are ready for
10
Practice questions!
Question # 1
+13
+
+7
Question # 2
-25
+
-15
Question # 3
+15+ -30
Question # 4
-20
+
+5
Question # 5
+45
+
-20
Question # 6
+100
-
+150
Question # 7
-50
-
-30
Question # 8
-14
-
-2
Question # 9
-12
-
+12
Question # 10
+2
-
-4
-
+2
+
+4
And now the answers.
Prepare
Yourself !
Question # 1
+13
+
+7
+20
=
Question # 2
-25
+
-15
-40
=
Question # 3
+15+ -30
-15
=
Question # 4
-20
+
+5
-15
=
Question # 5
+45
+
-20
+25
=
Question # 6
+100
-
+150
-50
=
Question # 7
-50
-
-30
-20
=
Question # 8
-14
-
-2
-12
=
Question # 9
-12
-
+12
-24
=
Question # 10
+2
-
-4
-
+2
+
= +8
+4
Almost…
The
End
Remember…
People do not wake up one
morning and know how to
tie their shoes!
It takes
Practice!
Now…
The
End