Finding the Fourth Proportional to 85.92, 128.79 and 82.05

Step by Step Solution

1. Step 1: Write the proportion equation
   85.92 : 128.79 = 82.05 : x
2. Step 2: Convert to fraction form
   85.92/128.79 = 82.05/x
3. Step 3: Cross multiply
   85.92x = 128.79 × 82.05
4. Step 4: Simplify right side
   85.92x = 10,567.22
5. Step 5: Solve for x
   x = 10,567.22/85.92
6. Step 6: Final answer
   x = 122.99