Finding the Fourth Proportional to 8,408.78, 12,608.78 and 3,139.45

Step by Step Solution

1. Step 1: Write the proportion equation
   8,408.78 : 12,608.78 = 3,139.45 : x
2. Step 2: Convert to fraction form
   8,408.78/12,608.78 = 3,139.45/x
3. Step 3: Cross multiply
   8,408.78x = 12,608.78 × 3,139.45
4. Step 4: Simplify right side
   8,408.78x = 39,584,640.27
5. Step 5: Solve for x
   x = 39,584,640.27/8,408.78
6. Step 6: Final answer
   x = 4,707.54