3 x 5 means… 3 “lots of” 5 3 x 5 means… 3 “lots of” 5 5 + 5 + 5 = 15
TRANSCRIPT
Multiplying and dividing integers
Multiplying and dividing integers
3 x 5 means…
Multiplying and dividing integers
3 x 5 means…
3 “lots of” 5
Multiplying and dividing integers
3 x 5 means…
3 “lots of” 5
5 + 5 + 5 = 15
Multiplying and dividing integers
3 x -5 means…
Multiplying and dividing integers
3 x -5 means…
3 “lots of” -5
Multiplying and dividing integers
3 x -5 means…
3 “lots of” -5
(-5) + (-5) + (-5) = -15
Multiplying and dividing integers
3 x -5 means…
3 “lots of” -5
(-5) + (-5) + (-5) = -15 Is there an easier way to
do this??
Multiplying and dividing integers
YES but first we need to learn this important
rule
Multiplying and dividing integers
positive x positive
negative x negative
positive x negative
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x 5 = ?
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x 5 = ?
Both of these are positive numbers so our answer must also be a positive
number
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x 5 = 15
In this case 3 x 5 = 15
(positive 15)
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x -5 = ?
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x -5 = ?
This time we have a positive times a negative
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x -5 = ?
Which we know means our answer must be a
negative number
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x -5 = ?3 x 5 = 15
So, first we multiply the numbers together
ignoring the signs…
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x -5 = ?3 x 5 = 15
…but we know our answer must be a negative
number…
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
3 x -5 = ?3 x 5 = 15
3 x -5 = -15
So our final answer looks like this
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
One more example:
-3 x -5 = ?
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
One more example:
-3 x -5 = ?
Negative times negative
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
One more example:
-3 x -5 = ?
Equals a positive answer
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
One more example:
-3 x -5 = ?3 x 5 = 15
…multiply the numbers (ignoring the signs)
Multiplying and dividing integerspositive x positive
negative x negative
positive x negative
One more example:
-3 x -5 = ?3 x 5 = 15-3 x -5 = 15
Then put the signs back inremebering that our answer here must be
positive
THEEND