Finding the Fourth Proportional to 86.15, 128.43 and 85.37

Step by Step Solution

1. Step 1: Write the proportion equation
   86.15 : 128.43 = 85.37 : x
2. Step 2: Convert to fraction form
   86.15/128.43 = 85.37/x
3. Step 3: Cross multiply
   86.15x = 128.43 × 85.37
4. Step 4: Simplify right side
   86.15x = 10,963.43
5. Step 5: Solve for x
   x = 10,963.43/86.15
6. Step 6: Final answer
   x = 127.27