Operations on Fractions - With Steps & Formulas
1. Adding Fractions
Rule:
• Same denominators: (a/b) + (c/b) = (a + c)/b
• Different denominators: Find the Least Common Denominator (LCD), convert, then add numerators.
Example 1: 1/2 + 1/3
Step 1: LCD of 2 and 3 is 6
Step 2: Convert → 1/2 = 3/6, 1/3 = 2/6
Step 3: Add → (3 + 2)/6 = 5/6
Example 2 (Same denominator): 3/4 + 2/4 = (3 + 2)/4 = 5/4 = 1 1/4
2. Subtracting Fractions
Rule:
Same as addition, but subtract the numerators.
Example: 3/4 - 1/6
Step 1: LCD of 4 and 6 is 12
Step 2: Convert → 3/4 = 9/12, 1/6 = 2/12
Step 3: Subtract → (9 - 2)/12 = 7/12
3. Multiplying Fractions
Rule (Very Easy):
(a/b) × (c/d) = (a × c) / (b × d)
No need for common denominator. Simplify before or after multiplying.
Example: 2/3 × 4/5
Multiply numerators: 2 × 4 = 8
Multiply denominators: 3 × 5 = 15
Result: 8/15 (already simplified)
Example with cancellation: 3/4 × 2/9 = (3×2)/(4×9) = 6/36 = 1/6
4. Dividing Fractions
Rule (Keep-Change-Flip):
(a/b) ÷ (c/d) = (a/b) × (d/c)
Flip the second fraction and multiply.
Example: 3/4 ÷ 2/5
Step 1: Flip 2/5 → 5/2
Step 2: Multiply → (3/4) × (5/2) = 15/8
Result: 15/8 or 1 7/8
Another Example: 1/2 ÷ 1/4 = (1/2) × (4/1) = 2