Finding the Fourth Proportional to 12,399.90, 16,815.48 and 12,399.90

Step by Step Solution

1. Step 1: Write the proportion equation
   12,399.90 : 16,815.48 = 12,399.90 : x
2. Step 2: Convert to fraction form
   12,399.90/16,815.48 = 12,399.90/x
3. Step 3: Cross multiply
   12,399.90x = 16,815.48 × 12,399.90
4. Step 4: Simplify right side
   12,399.90x = 208,510,270.45
5. Step 5: Solve for x
   x = 208,510,270.45/12,399.90
6. Step 6: Final answer
   x = 16,815.48