Finding the Fourth Proportional to 85.38, 128.05 and 39.69

Step by Step Solution

1. Step 1: Write the proportion equation
   85.38 : 128.05 = 39.69 : x
2. Step 2: Convert to fraction form
   85.38/128.05 = 39.69/x
3. Step 3: Cross multiply
   85.38x = 128.05 × 39.69
4. Step 4: Simplify right side
   85.38x = 5,081.61
5. Step 5: Solve for x
   x = 5,081.61/85.38
6. Step 6: Final answer
   x = 59.52