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Published bySpencer Hilary Elliott Modified over 7 years ago

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**Subtracting Positive and Negative Integers**

Magic Bean Method

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**Magic Bean Model Green chips or tiles represent a positive 1**

Red chips or tiles represent a negative 1 One of each tile represents a “zero pair” -1 +1

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**Modeling -3 - (+4) = -7 Add three red “beans” to represent -3**

Now we have to subtract 4 positive “beans” from the zero pairs to represent the +4. The negative beans that are left now float up for an answer of -7. When subtracting using the Magic Bean Model, you have to keep some “zero pairs” (which equal zero, so have no value) to borrow from in the bottom of the “jar”.

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**Modeling 2 – (-4) Add two green beans to represent the positive 2.**

Now subtract 4 negative “beans” from the zero pairs to represent the -4. The unmatched “beans” will float to the top for an answer of +6. Start with the zero pairs.

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**Rules for Subtracting Integers**

You can also use all of your rules for ADDING integers by doing a simple change. When we divide fractions, we really just flip and multiply. Similarly, when we subtract integers, we change the sign and add. The Rule to Remember: KEEP, FLIP, FLIP

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KEEP, FLIP, FLIP Example: − 3 − (− 4) KEEP the – sign in front of the 3. FLIP the next – sign to a +. Flip the next – sign to a +. You are left with an integer addition problem: − 3 + (+4) = 1

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KEEP, FLIP, FLIP One more KEEP, FLIP, FLIP Example: 4 – (+2) KEEP the implied + sign in front of the 4. FLIP the negative sign. FLIP the positive sign. You are left with an integer addition problem: 4 + (-2) = 2

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