2. ADDING AND SUBTRACTING FRACTIONS WITH UNLIKE DENOMINATORS! BECAUSE YOU NEVER KNOW WHEN THE WORLD WILL GO CRAZY, DECIDE TO GET RID OF DECIMALS, AND FORCE YOU TO BUY THINGS PRICED AS FRACTIONS…

3. LET’S LOOK BACK AT HOW WE ADD FRACTIONS WITH LIKE DENOMINATORS

5. BUT WHAT ABOUT UNLIKE DENOMINATORS?

6. WHEN ADDING FRACTIONS WITH UNLIKE DENOMINATORS, WE USE THE LCM METHOD LCM stands for Love Cute Monkeys Just kidding… It stands for Least Common Multiple method. We need to figure out how to get the piece sizes the same so that we can add the numerators easily On this problem, we only have to alter the piece size of one of our models. Which one do you think we need to change the piece size of. Why?

7. THE LEAST COMMON MULTIPLE METHOD MAKES IT EASIER….BECAUSE WE DON’T NEED NO STINKIN’ PICTURES!!!! 1. First write the problem like this 2. Write both denominators here 8 4 3. Fill in MULTIPLES of each denominator until you find a match between the two lines 16 24 32 8 12 16 4. LOOK! We already have 2 matches NOT THE 16 5.Use the LEAST COMMON MULTIPLE which is the 8 NOT THE 16

8. LCM (CONTINUED) SO WHAT DO WE DO WITH THE 8 WE GOT? 8 4 16 24 32 8 12 16 1. Make it the new denominators 3. Multiply the denominator and numerator of the top fraction by THAT number! 2. For the first fraction Ask: How many times do I multiply the original denominator to get the new denominator? x1 x2 x1 7 4. Repeat steps 2 & 3 with the 2 nd fraction. x2 2 5. Add your new EQUIVALENT FRACTIONS normally 6. Last step! Simplify your answer if needed! =

9. USE THE LCM METHOD TO SIMPLIFY THE FOLLOWING EXPRESSION: 7 4 14 21 28 812 16 1. Find the LCM and make it the new denominators 3. Multiply the denominator and numerator of the top fraction by THAT number! 2. For the first fraction Ask: How many times do I multiply the original denominator to get the new denominator? x4 x7 x4 24 4. Repeat steps 2 & 3 with the 2 nd fraction. x7 21 5. Add your new EQUIVALENT FRACTIONS normally 6. Last step! Simplify your answer if needed! = 35 20 24 28

10. BRAIN BREAK

11. USE THE LCM METHOD TO SIMPLIFY THE FOLLOWING EXPRESSION: 6 8 12 18 24 1624 32 1. Find the LCM and make it the new denominators 3. Multiply the denominator and numerator of the top fraction by THAT number! 2. For the first fraction Ask: How many times do I multiply the original denominator to get the new denominator? x4 x3 x4 12 4. Repeat steps 2 & 3 with the 2 nd fraction. x3 21 5. Add your new EQUIVALENT FRACTIONS normally 6. Last step! Simplify your answer if needed! = 30 40 48 56 =

12. USE THE LCM METHOD TO SIMPLIFY THE FOLLOWING EXPRESSION: 9 6 18 27 36 1218 24 1. Find the LCM and make it the new denominators 3. Multiply the denominator and numerator of the top fraction by THAT number! 2. For the first fraction Ask: How many times do I multiply the original denominator to get the new denominator? x2 x3 x2 14 4. Repeat steps 2 & 3 with the 2 nd fraction. x3 3 5. Add your new EQUIVALENT FRACTIONS normally 6. Last step! Simplify your answer if needed! 45 30 36 42

13. CONGRATULATIONS YOU SURVIVED!!!