Finding the Fourth Proportional to 86.38, 129.48 and 78.82

Step by Step Solution

1. Step 1: Write the proportion equation
   86.38 : 129.48 = 78.82 : x
2. Step 2: Convert to fraction form
   86.38/129.48 = 78.82/x
3. Step 3: Cross multiply
   86.38x = 129.48 × 78.82
4. Step 4: Simplify right side
   86.38x = 10,205.61
5. Step 5: Solve for x
   x = 10,205.61/86.38
6. Step 6: Final answer
   x = 118.15