1. Learning Target:Students will learn how to compute the actual sums and differences of fractions with different denominators.

2. BIG IDEA:YOU MUST FIND COMMON DENOMINATORSthen follow the same rules as we did when we had fractions with common denominators to begin with.

3. Why is it so important to find a common denominator when adding and subtracting fractions?

4. A: so you can truly understand the relationship between your two fractions.

5. To find common denominators you can either find the LCD or you can us the method below.http://www.mathsisfun.com/numbers/common-denominator.html

6. Video of the method described on the last slide.http://www.mathsisfun.com/numbers/common-denominator.html

7. Find the sum or difference.3/4 + 2/35/6 + 7/107/8 – 1/41/2 – 4/9Remember to simplify your answer.

8. Find the sum or difference.3/4 + 2/3 = 1 5/125/6 + 7/10 = 1 8/15 7/8 – 1/4 = 5/81/2 – 4/9 = 1/18Remember to simplify your answer.

9. Evaluate the expression.2/3 + 1/3 + 3/71/4 + 1/6 – 1/311/12 – (1/4 + 1/6)

10. Evaluate the expression.2/3 + 1/3 + 3/7 = 1 3/71/4 + 1/6 – 1/3 = 1/1211/12 – (1/4 + 1/6) = 1/2

11. When in life will you ever add or subtract fractions?

12. A: Finding the perimeter of an object.CookingCarpentry workPharmacist Figuring how much gas you need to fill your gas tank.

13. Can you compute the actual sums and differences of fractions with different denominators?