1. Fun with Fractions

2. Important…. It is important that you are able to make calculations with fractions. You must be able to add, subtract, multiply, and divide fractions to be successful with projects. Let’s calculate the total length of several boards…

3. ADD To add fractions, you must determine a common denominator. In this case, it is 4. Once the numerator and denominator are correct, add the numerators together and divide by the denominator. One board is 1½’ and the other is ¾’, what is total length of the board? 1 + ½ + ¾ =

4. ADD 1 + ½ + ¾ = 4/4 + 2/4 + ¾ = 9/4 = 2¼’

5. SUBTRACT To subtract fractions, you must also determine a common denominator. In this case, it is 8. Once the numerator and denominator are correct, subtract the numerators and (when necessary divide by the denominator). One board is ⅞” and we’ll subtract ¼”. What is the total now?

6. SUBTRACT ⅞ − ¼ = 7/8 − 2/8 = ⅝”

7. MULTIPLY To multiply fractions, you may multiply the numerator and denominator straight across. Multiply these two fractions: 1/16” × ¾”. What is the total?

8. MULTIPLY 1 3 3” --- × --- = --- 16 4 64

9. DIVIDE To divide fractions, turn the second fraction (the number you wan t to divide by) upside down–flip. In this case, 15/16ths becomes 16/15ths. Then, multiply the numerators and then the denominators. Reduce 48/240 to ⅕ by using the greatest common factor: In this case 48. Divide the numerator by 48 and then divide the denominator by 48. Divide 3/16 by 15/16.

10. DIVIDE 3 15 --- ÷ --- = 16 3 16 48 1” --- × --- = ---- = --- 16 15 240 5

11. Practice Time… Addition: 1.3/32 + 5/8 + ¼ = 2.½ + 5/16 + 3/8 + ¾ = 3.9/10 + 7/20 + 3/5 = Subtraction: 4.7/8 − 5/16 5.23/32 − 15/32 6.¾ − (1/16 × 1/16) = Multiplication: 7.3/32 × 7/8 = 8.1/16 × 1/8 × ¾ = 9.(17/32) (9/10) = Division: 10.¾ ÷ 1/16 11.21/64 ÷ (3/16 − 1/8) = 12.99/100 ÷ 3/10 =