Finding the Fourth Proportional to 85.69, 128.42 and 54.83

Step by Step Solution

1. Step 1: Write the proportion equation
   85.69 : 128.42 = 54.83 : x
2. Step 2: Convert to fraction form
   85.69/128.42 = 54.83/x
3. Step 3: Cross multiply
   85.69x = 128.42 × 54.83
4. Step 4: Simplify right side
   85.69x = 7,040.70
5. Step 5: Solve for x
   x = 7,040.70/85.69
6. Step 6: Final answer
   x = 82.17