Finding the Fourth Proportional to 21,078.38, 31,608.30 and 11,215.31

Step by Step Solution

1. Step 1: Write the proportion equation
   21,078.38 : 31,608.30 = 11,215.31 : x
2. Step 2: Convert to fraction form
   21,078.38/31,608.30 = 11,215.31/x
3. Step 3: Cross multiply
   21,078.38x = 31,608.30 × 11,215.31
4. Step 4: Simplify right side
   21,078.38x = 354,496,913.34
5. Step 5: Solve for x
   x = 354,496,913.34/21,078.38
6. Step 6: Final answer
   x = 16,818.04