Computing with Parts: Fraction Operations
Fraction operations β addition, subtraction, multiplication, and division β extend the four basic arithmetic operations to numbers expressed as parts of a whole. Mastering these operations lets students combine measurements, scale recipes, split quantities, and solve equations that involve non-whole amounts.
Components of Fraction Operations
This section covers the four operations with fractions:
- Adding Fractions: Find a common denominator, add the numerators, and simplify the result.
- Subtracting Fractions: Find a common denominator, subtract the numerators, and simplify.
- Multiplying Fractions: Multiply numerators together and denominators together, then simplify.
- Dividing Fractions: Multiply by the reciprocal of the divisor (flip and multiply), then simplify.
Examples of Fraction Operations
Adding Fractions Examples
- Add 1/4 + 2/4: Same denominator, so add numerators: 1 + 2 = 3, giving 3/4.
- Add 2/3 + 1/5: The LCM of 3 and 5 is 15, so rewrite as 10/15 + 3/15 = 13/15.
- A trail mix recipe uses 1/3 cup of nuts and 1/6 cup of raisins. Rewrite 1/3 as 2/6, then add 2/6 + 1/6 = 3/6, which simplifies to 1/2 cup total.
Subtracting Fractions Examples
- Subtract 5/8 - 3/8: Same denominator, so 5 - 3 = 2, giving 2/8, which simplifies to 1/4.
- Subtract 3/4 - 1/3: The LCM of 4 and 3 is 12, so rewrite as 9/12 - 4/12 = 5/12.
- A water bottle was 7/10 full and you drank 2/5. Rewrite 2/5 as 4/10, then 7/10 - 4/10 = 3/10 remaining.
Multiplying Fractions Examples
- Multiply 2/3 Γ 4/5: Multiply numerators 2 Γ 4 = 8 and denominators 3 Γ 5 = 15, giving 8/15.
- Multiply 3/4 Γ 2/9: Multiply to get 6/36, then simplify by dividing both by 6 to get 1/6.
- A garden plot is 3/4 acre, and you plant flowers on 2/3 of it. The flower area is 3/4 Γ 2/3 = 6/12 = 1/2 acre.
Dividing Fractions Examples
- Divide 3/4 Γ· 1/2: Flip the second fraction and multiply, 3/4 Γ 2/1 = 6/4, which simplifies to 3/2 or 1 1/2.
- Divide 5/6 Γ· 2/3: Flip and multiply, 5/6 Γ 3/2 = 15/12, which simplifies to 5/4 or 1 1/4.
- A board 7/8 meter long is cut into pieces of 1/4 meter each. Divide 7/8 Γ· 1/4 = 7/8 Γ 4/1 = 28/8 = 3 1/2 pieces.