Finding the Fourth Proportional to 93.31, 128.78 and 78.73

Step by Step Solution

1. Step 1: Write the proportion equation
   93.31 : 128.78 = 78.73 : x
2. Step 2: Convert to fraction form
   93.31/128.78 = 78.73/x
3. Step 3: Cross multiply
   93.31x = 128.78 × 78.73
4. Step 4: Simplify right side
   93.31x = 10,138.85
5. Step 5: Solve for x
   x = 10,138.85/93.31
6. Step 6: Final answer
   x = 108.66