Finding the Fourth Proportional to 8,105.20, 12,138.60 and 8,105.20

Step by Step Solution

1. Step 1: Write the proportion equation
   8,105.20 : 12,138.60 = 8,105.20 : x
2. Step 2: Convert to fraction form
   8,105.20/12,138.60 = 8,105.20/x
3. Step 3: Cross multiply
   8,105.20x = 12,138.60 × 8,105.20
4. Step 4: Simplify right side
   8,105.20x = 98,385,780.72
5. Step 5: Solve for x
   x = 98,385,780.72/8,105.20
6. Step 6: Final answer
   x = 12,138.60