Finding the Fourth Proportional to 86.05, 128.31 and 82.29

Step by Step Solution

1. Step 1: Write the proportion equation
   86.05 : 128.31 = 82.29 : x
2. Step 2: Convert to fraction form
   86.05/128.31 = 82.29/x
3. Step 3: Cross multiply
   86.05x = 128.31 × 82.29
4. Step 4: Simplify right side
   86.05x = 10,558.63
5. Step 5: Solve for x
   x = 10,558.63/86.05
6. Step 6: Final answer
   x = 122.70