Finding the Fourth Proportional to 86.18, 128.57 and 82.35

Step by Step Solution

1. Step 1: Write the proportion equation
   86.18 : 128.57 = 82.35 : x
2. Step 2: Convert to fraction form
   86.18/128.57 = 82.35/x
3. Step 3: Cross multiply
   86.18x = 128.57 × 82.35
4. Step 4: Simplify right side
   86.18x = 10,587.33
5. Step 5: Solve for x
   x = 10,587.33/86.18
6. Step 6: Final answer
   x = 122.86