Transcript Positive and Negative Numbers

Positive and Negative Numbers
by Mr. Russo
We know when we see
positive numbers,
but when do we use
or see negative
numbers?
Negative Numbers Are Used to
Measure Temperature
Negative Numbers Are Used to
Measure Under Sea Level
30
20
10
0
-10
-20
-30
-40
Negative Numbers Are Used to
Show Debt
Let’s say you wanted your parents to buy
you a video game. They loaned you $50.
You buy your game and enjoy it. However,
you still owe Mom & Dad $50. Your current
balance or debt is -$50.
Definition
• Positive number – a number
greater than zero.
0 1 2 3 4 5 6
Definition
• Negative number – a number
less than zero.
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Definition
• Opposite Numbers – numbers
that are the same distance from
zero in the opposite direction
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Positive & Negative Numbers
Working with positive and negative
numbers is like driving in traffic.
You have to watch the traffic signs
and follow the driving rules.
Solve the Problems
• -3 + -5 =
-8
11
•4+7=
• (+3) + (+4) = 7
-13
• -6 + -7 =
14
•5+9=
-18
• -9 + -9 =
Addition Rules
• Rule #1 – If the signs are the
same, pretend the signs aren’t
there. Add the numbers together
and re-attach the sign you started
with.
9 + 5 = 14
-9 + -5 = -14
Solve the Problems
• 3 + -5 =
-2
3
• -4 + 7 =
-1
• (3) + (-4) =
1
• -6 + 7 =
-4
• 5 + -9 =
0
• -9 + 9 =
Integer Addition Rules
• Rule #2 – If the signs are
different, subtract the two
numbers and take the sign of the
larger number.
-9 + 5 =
9 - 5 = 4 Answer = - 4
Larger number
Independent Practice
• Math Journal p. 232-233
• Once finished, you can try the Math
challenge games on Mr. Russo's Website