Adding and Subtracting Integers Foundations of Algebra

Review Positive and Negatives! Write the integer that best represents each of the following situations.  Tori’s spent way too much money and is now in the hole $50.  Emerald received her allowance of $  Mr. Walker went to the beach on a bright and sunny day. The temperature was 80 degrees outside.  Ryan owes his brother $ Put the following temperatures in order from coldest to hottest.  California 70 o F  Anchorage 32 o F  Antartica -40 o F  Honolulu 83 o F  Sydney 72 o F  Amsterdam 35 o F  South Pole -55 o F

Examples: Use the number line if necessary. 1) (-4) + 8 = 4 2) (-1) + (-3) = -4 3) 5 + (-7) = -2

Addition Rule 1) When the signs are the same, ADD and keep the sign. (-2) + (-4) = -6 2) When the signs are different, SUBTRACT and use the sign of the larger number. (-2) + 4 = (-4) = -2

Karaoke Time! Addition Rule: Sung to the tune of “Row, row, row, your boat” Same signs add and keep, different signs subtract, keep the sign of the higher number, then it will be exact!

The additive inverses (or opposites) of two numbers add to equal zero. Example: The additive inverse of 3 is -3 Proof: 3 + (-3) = 0 We will use the additive inverses for subtraction problems.

What’s the difference between and 7 + (-3) ? = 4 and 7 + (-3) = 4 The only difference is that is a subtraction problem and 7 + (-3) is an addition problem. “SUBTRACTING IS THE SAME AS ADDING THE OPPOSITE.” (Keep-change-change)

When subtracting, change the subtraction to adding the opposite (keep-change-change) and then follow your addition rule. Example #1: (-7) (+7) Diff. Signs --> Subtract and use larger sign. 3 Example #2: (-7) Same Signs --> Add and keep the sign. -10

Here’s one with a variable! Example #3: 11b - (-2b) 11b + (+2b) Same Signs --> Add and keep the sign. 13b

The temperature in Allentown, PA was -20 C at 6 am. By noon that day the temperature had risen 19 C. By 6pm, the temperature had fallen 13 C. What was the temperature at 6pm?

Emily has $151 in her checking account. She writes a check for $117, makes a deposit of $49, then writes a check for $81. find the amount left in her account

The highest location in a Italy is 15,586 feet above sea level. The lowest point in the same country is 239 feet below sea level. a) Find the difference in the two elevations. + 15, , ,825 b) Milan, Italy is at 6,886 feet above sea level. Is this closer to the highest point or the lowest point?

Extra Practice = = (-89) = = 72 + (-92) = (+47) = (-61) = (+78) = = = (-31) = = 95 + (-58) = (-47) = 62 + (+69) = (-53) = = (-1) =