Presentation on theme: "Subtracting Positive and Negative Integers"— Presentation transcript:
1 Subtracting Positive and Negative Integers Magic Bean Method
2 Magic Bean Model Green chips or tiles represent a positive 1 Red chips or tiles represent a negative 1One of each tile represents a “zero pair”-1+1
3 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”.
4 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.
5 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
6 KEEP, FLIP, FLIPExample: − 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
7 KEEP, FLIP, FLIPOne 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