Finding the Fourth Proportional to 85.61, 128.39 and 39.31

Step by Step Solution

1. Step 1: Write the proportion equation
   85.61 : 128.39 = 39.31 : x
2. Step 2: Convert to fraction form
   85.61/128.39 = 39.31/x
3. Step 3: Cross multiply
   85.61x = 128.39 × 39.31
4. Step 4: Simplify right side
   85.61x = 5,046.49
5. Step 5: Solve for x
   x = 5,046.49/85.61
6. Step 6: Final answer
   x = 58.95