Finding the Fourth Proportional to 8,426.88, 12,638.08 and 5,128.56

Step by Step Solution

1. Step 1: Write the proportion equation
   8,426.88 : 12,638.08 = 5,128.56 : x
2. Step 2: Convert to fraction form
   8,426.88/12,638.08 = 5,128.56/x
3. Step 3: Cross multiply
   8,426.88x = 12,638.08 × 5,128.56
4. Step 4: Simplify right side
   8,426.88x = 64,815,151.56
5. Step 5: Solve for x
   x = 64,815,151.56/8,426.88
6. Step 6: Final answer
   x = 7,691.48