Finding the Fourth Proportional to 21,628.56, 29,849.48 and 13,128.73

Step by Step Solution

1. Step 1: Write the proportion equation
   21,628.56 : 29,849.48 = 13,128.73 : x
2. Step 2: Convert to fraction form
   21,628.56/29,849.48 = 13,128.73/x
3. Step 3: Cross multiply
   21,628.56x = 29,849.48 × 13,128.73
4. Step 4: Simplify right side
   21,628.56x = 391,885,840.43
5. Step 5: Solve for x
   x = 391,885,840.43/21,628.56
6. Step 6: Final answer
   x = 18,118.90