Finding the Fourth Proportional to 78.91, 108.86 and 54.31

Step by Step Solution

1. Step 1: Write the proportion equation
   78.91 : 108.86 = 54.31 : x
2. Step 2: Convert to fraction form
   78.91/108.86 = 54.31/x
3. Step 3: Cross multiply
   78.91x = 108.86 × 54.31
4. Step 4: Simplify right side
   78.91x = 5,911.77
5. Step 5: Solve for x
   x = 5,911.77/78.91
6. Step 6: Final answer
   x = 74.92