Download Adding and Subtracting Integers

Adding and Subtracting
Integers
“All things excellent are as difficult as they are rare”
Spinoza
Remember numbers can be positive or negative
NO SIGN MEANS POSITIVE
• “ – ” means the number is negative
• “ + ” means the number is positive
• No sign usually means the number is really a
positive number.
• Example 5 is really +5
Adding and Subtracting positive numbers is just
simple addition and subtraction
Example: 2 + 3 = 5
is really saying
"Positive 2 plus Positive 3 equals Positive 5"
You could write it as (+2) + (+3) = (+5)
AND….
Example: 6 − 3 = 3
is really saying
"Positive 6 minus Positive 3 equals Positive 3"
You could write it as (+6) − (+3) = (+3)
Balloons and Weights
This basket has balloons and weights
tied to it:
1)The balloons pull up (POSITVE)
2) And the weights drag down
(NEGATIVE)
Here is what adding and subtracting positive
numbers looks like
You can add balloons (you are
adding positive value)
THE BASKET GETS PULLED
UPWARDS (POSITIVE)
Or you can take away balloons
The basket gets
pulled down
What if you add negative numbers?
You can add weights ( you
are adding negative values
The basket gets pulled
downwards (NEGATIVE)
What if you subtract negative numbers?
You take away weights
(you are subtracting
negative values)
The basket gets pulled
upwards (POSITIVE)
So….
Subtracting a Negative
made the basket GO UP!?!
So subtracting a Negative
is the same as Adding!!!!
General Rule for SUBTRACTING integers
Example
What is 6 – (-3) ?
6 – (-3) = 6 + 3 = 9
NOW…. Solve
1)14 – (-4)
2)20 – (-10)
3)15 – (-29)
And Positive and Negative Together…
Subtracting a
positive
or
Adding a negative is
SUBTRACTION
Example
1) What is 6 – (+3) ?
6 – (+3) = 6 – 3 = 3
2) What is 5 + (-7) ?
5 + (-7) = 5 – 7 = -2
Now solve…
1. 6 + -8
2. 10 + -5
3. 35 + -55
The Rules
Two like signs become a positive
sign
Two unlike signs become a
negative sign
Example
+ (+):3 + (+2) = 3 + 2 = 5
- ( - ): 6 – (-3) = 6 + 3 = 9
+ ( - ): 7 + (-2) = 7 – 2 = 5
- ( + ): 8 – (+2) = 8 – 2 = 6
So, all you have to remember is
• Two LIKE signs become a POSITVE
sign
• Two UNLIKE signs become a
NEGATIVE sign
LET’S WATCH A VIDEO
https://www.youtube.com/watch?v=lBscLuttQq0
Exit Ticket
1) 43 – (-23)
2) 19 + - 38
3) -27 + 33
CHALLENGE:
1) -3.16 + 14
2) 13.4 – (-3.4)