SLO
Know how to multiply and
divide negative numbers
-6 x –4
=
http://www.khanacademy.org/math/arith
metic/absolutevalue/mult_div_negatives/v/multiplyingpositive-and-negative-numbers (Khan:
multiply negative numbers video)
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Multiplying integers
5 x -3
this can be thought of as 5 lots of -3
–3 + –3 + –3 + –3 + –3 = –15
–3
–15
–3
–12
–3
–9
–3
–6
–3
–3
0
5 × –3 = –15
A positive number × a negative number = a negative number
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Multiplying negative numbers
–7 × 3 = 3 × –7 = –21
–7
–21
–7
–7
–14
–7
0
A negative number × a positive number = a negative number
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Multiplying negative numbers
–4 × –6 = 24
0
– –6
– –6
– –6
6
12
– –6
18
24
A negative number × a negative number = a positive number
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Rules for multiplying and dividing
When multiplying negative numbers remember:
+ × + = +
+ × – = –
– × + = –
– × –
= +
When we are dividing negative numbers similar rules apply:
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+ ÷
+ = +
+ ÷
– = –
– ÷
+ = –
– ÷
–
= +
Multiplying/Dividing
Integers
Copy into
your
notes
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1st Number
2nd Number
Answer
+
–
–
+
+
–
+
–
+
+
–
–
Copy into
note book
A way to Remember!
To remember whether your answer will be
positive or negative when multiplying or dividing,
use:
Mr. Multiplivision
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Copy into
your
notes
E.g. 1
5x
-3
Cover the two signs you are using
The one that is left is
the sign of the answer?
=
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-15
E.g. 2
-48  -4
Cover the two signs you are using
= +12
The sign that is left
is the sign of the
answer?
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Your Turn
(1) – 2 × 8 =
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-16
(7) 5 × - 7 =
-35
(2) – 4 × - 7 = 28
(8) – 7 × - 8 = 56
(3) 5 × - 6 = -30
(9) – 20 × 10 = -200
(4) – 4 × - 3 = 12
(10) 2 2 × -3 = -66
(5) – 7 × 10 = -70
(11) – 20 × -10 = 200
(6) 1 2 × - 2 = -24
(12) 12 × 9 =
108
Your Turn:
Complete the following:
–3 × 8 = –24
–36 ÷
42 ÷
–7 = –6
540 ÷ –90 = –6
–12 × –8 = 96
–7 × –25 = 175
47 ×
–4 × –5 × –8 = –160
3
= 141
–72 ÷ –6 =
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12
9
= –4
3 × –8 ÷ –16 = 1.5
Mixed division square
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Mixed multiplication square
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Mixed division square
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SLO
Learn how to multiply several
negative numbers together
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Copy into
note book
Multiplying Several Integer Factors
a. (-1) x (+1) x (-1) = +1
b. (+1) x (+1) x (-1) = -1
If there is an
even number of
negative signs,
the product is
positive
c. (-1) x (-1) x (+1) = +1
d. (-1) x (-1) x (-1) = -1
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If there is an
odd number of
negative signs,
the product is
negative
Your Turn
1) (-1) x (+1) x (-1) = +1
2) (+1) x (+1) x (-1) = -1
3) (-1) x (-1) x (+1) = +1
4) (-1) x (-1) x (-1) = -1
5) (-1) x (-1) x (+1) x (-1) x (+1) = -1
6) (-1) x (+1) x (+1) x (-1) x (+1) = +1
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Your Turn:
Multiplying Several Integer Factors
a. (-1) x (+1) x (-1) x (+1) = 1
b. (+1) x (+1) x (-1) x(-1) = 1
c. (-1) x (+1) x (-1) x (-1) x (+1) = -1
d. (-1) x (-1) x (-1) x (-1) x (+1) x (-1) = -1
e. (1) x (+1) x (-1) x (-1) x (+1) x (-1) = -1
f. (-1) x (-1) x (-1) x (-1) x (-1) x (-1) = 1
g. (-2) x (-3) x (-2) x (+1) = -12
h. (-1) x (-3) x (-2) x (-2) x (-3) = -36
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Your Turn
1) (-2) x (+2) x (-1) x (-3)= -12
2) (+1) x (+4) x (-5) = -20
3) (-17) x (-2) x (+2) = 68
4) (-2) x (-3) x (-6) x (4) = -144
5) (-2) x (-3) x (-3) = -18
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Integer cards – multiplication and division
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Number spiral
–10
–8
–4
2
–11
3
–15
0
–3
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–16
6
–2
SLO
BEDMAS (order of operations)
and negative numbers
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Copy into
note book
Order of Operations With Integers
BEDMAS is always used with negative numbers
E.g.
3 x (–7) + 4 x (-5) = -21 + -20 = -41
15 + (+5)2 x 2 = 15 + 25x2 = 15 + 50 = 65
(-18) – (-3)2 – 9 x 2 = -18 – 9 – 18 = -45
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