Finding the Fourth Proportional to 13,021.88, 19,520.77 and 5,128.69

Step by Step Solution

1. Step 1: Write the proportion equation
   13,021.88 : 19,520.77 = 5,128.69 : x
2. Step 2: Convert to fraction form
   13,021.88/19,520.77 = 5,128.69/x
3. Step 3: Cross multiply
   13,021.88x = 19,520.77 × 5,128.69
4. Step 4: Simplify right side
   13,021.88x = 100,115,892.05
5. Step 5: Solve for x
   x = 100,115,892.05/13,021.88
6. Step 6: Final answer
   x = 7,688.28