Adding Integers
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Transcript of Adding Integers
Adding Integers
Mrs. YoungEMC 1
Problem
• George owes his friend Jeanne $3. If he borrows another $6, how much will he owe her altogether?– Now I know that you are thinking this is
simple, but just wait!
Solution
• Actually, this problem is quite simple: just add $3 and $6 and the result is $9.
• However, the problem can be solved using addition of integers. – Owing $3 can be represented by -3 and
owing $6 can be represented by -6. • The problem becomes:
-3 + -6 = -9
Let’s Use A Number Line!
• Look at the number line below: – Start at 0– Move to the left 3 spaces (why left???)– Move 6 more spaces to the left (why???)– We end at -9
• So -3 + -6 = -9
Let’s Try Another!
• How can we solve +5 + -3???– Simple! Use a number line!
• Start at 0• Move to the right 5 spaces (why right??)• Now move 3 spaces to the left (why left??)
– You can see that +5 + -3 = +2
Let’s Try One More!
• Solve -5 + 3– Start at 0– Move to the left 5 spaces (why??)– Now move 3 spaces to the right (why?)
• You can see that we end up at -2!
Let’s Check Out Some Rules!
• When adding integers that have the same sign, the answer will have the same sign.– For example: The sum of two negative
integers is a negative integer.
Adding Negative Integers
Integers Sum
-2 + -9 = -11
-5 + -8 = -13
-13 + -7 = -20
Rules Continued…
• Also, when adding two positive integers, the answer will be a positive integer.
Adding Positive Integers
Integers Sum
+2 + +9 = +11
+17 + +5 = +22
+29 + +16 = +45
Uh oh! Wait!
• But, what if I want to add a positive integer and a negative integer… what should I do??
• It’s simple!• Follow these steps:
1. Find the absolute value of each integer.
2. Subtract the smaller number from the larger number you get in Step 1.
3. The result from Step 2 takes the sign of the integer with the greater absolute value.
Let’s Try It!
• We can use a number line, or you don’t have to!– Solve +7 + -3
• Always start at 0• Move to the ____________ 7 spaces• Then move to the ________ 3 spaces
Let’s do it without the number line!
1. Find the absolute value of -7 and the absolute value of +3 (7 and 3)
2. Subtract the smaller number from the larger number in the Step 1 (7 – 3)
3. The result from Step 2 takes the sign of the integer with the greater absolute value.
• The answer would be -4 because the integer with the greater absolute value is negative!
Try this one!
• Solve -9 and +5. • Use a number line or not!1. Find the absolute value of -9 and the
absolute value of +52. Subtract the smaller number from the
larger number in the Step 13. The result from Step 2 takes the sign of
the integer with the greater absolute value.
• And the answer is……
Yep! You’re right!
-4
Here’s a Song For You!
(to the tune of “Row, row, row your boat”)
"Same Sign, Add and keep,Different sign, subtract.
Take the sign of the higher number
Then it'll be exact!"