Finding the Fourth Proportional to 21,111.57, 29,134.50 and 12,728.61

Step by Step Solution

1. Step 1: Write the proportion equation
   21,111.57 : 29,134.50 = 12,728.61 : x
2. Step 2: Convert to fraction form
   21,111.57/29,134.50 = 12,728.61/x
3. Step 3: Cross multiply
   21,111.57x = 29,134.50 × 12,728.61
4. Step 4: Simplify right side
   21,111.57x = 370,841,542.37
5. Step 5: Solve for x
   x = 370,841,542.37/21,111.57
6. Step 6: Final answer
   x = 17,565.80