Finding the Fourth Proportional to 21,390.78, 29,520.39 and 12,895.61

Step by Step Solution

1. Step 1: Write the proportion equation
   21,390.78 : 29,520.39 = 12,895.61 : x
2. Step 2: Convert to fraction form
   21,390.78/29,520.39 = 12,895.61/x
3. Step 3: Cross multiply
   21,390.78x = 29,520.39 × 12,895.61
4. Step 4: Simplify right side
   21,390.78x = 380,683,288.89
5. Step 5: Solve for x
   x = 380,683,288.89/21,390.78
6. Step 6: Final answer
   x = 17,796.61