Finding the Fourth Proportional to 85.58, 128.37 and 39.92

Step by Step Solution

1. Step 1: Write the proportion equation
   85.58 : 128.37 = 39.92 : x
2. Step 2: Convert to fraction form
   85.58/128.37 = 39.92/x
3. Step 3: Cross multiply
   85.58x = 128.37 × 39.92
4. Step 4: Simplify right side
   85.58x = 5,123.89
5. Step 5: Solve for x
   x = 5,123.89/85.58
6. Step 6: Final answer
   x = 59.88