Finding the Fourth Proportional to 86.05, 128.39 and 72.55

Step by Step Solution

1. Step 1: Write the proportion equation
   86.05 : 128.39 = 72.55 : x
2. Step 2: Convert to fraction form
   86.05/128.39 = 72.55/x
3. Step 3: Cross multiply
   86.05x = 128.39 × 72.55
4. Step 4: Simplify right side
   86.05x = 9,314.69
5. Step 5: Solve for x
   x = 9,314.69/86.05
6. Step 6: Final answer
   x = 108.25