Finding the Fourth Proportional to 12,815.52, 19,191.15 and 8,121.30

Step by Step Solution

1. Step 1: Write the proportion equation
   12,815.52 : 19,191.15 = 8,121.30 : x
2. Step 2: Convert to fraction form
   12,815.52/19,191.15 = 8,121.30/x
3. Step 3: Cross multiply
   12,815.52x = 19,191.15 × 8,121.30
4. Step 4: Simplify right side
   12,815.52x = 155,857,086.50
5. Step 5: Solve for x
   x = 155,857,086.50/12,815.52
6. Step 6: Final answer
   x = 12,161.59