Finding the Fourth Proportional to 85.86, 128.52 and 72.09

Step by Step Solution

1. Step 1: Write the proportion equation
   85.86 : 128.52 = 72.09 : x
2. Step 2: Convert to fraction form
   85.86/128.52 = 72.09/x
3. Step 3: Cross multiply
   85.86x = 128.52 × 72.09
4. Step 4: Simplify right side
   85.86x = 9,265.01
5. Step 5: Solve for x
   x = 9,265.01/85.86
6. Step 6: Final answer
   x = 107.91