Finding the Fourth Proportional to 21,115.38, 31,665.12 and 8,628.72

Step by Step Solution

1. Step 1: Write the proportion equation
   21,115.38 : 31,665.12 = 8,628.72 : x
2. Step 2: Convert to fraction form
   21,115.38/31,665.12 = 8,628.72/x
3. Step 3: Cross multiply
   21,115.38x = 31,665.12 × 8,628.72
4. Step 4: Simplify right side
   21,115.38x = 273,229,454.25
5. Step 5: Solve for x
   x = 273,229,454.25/21,115.38
6. Step 6: Final answer
   x = 12,939.83