Finding the Fourth Proportional to 100.91, 139.46 and 76.31

Step by Step Solution

1. Step 1: Write the proportion equation
   100.91 : 139.46 = 76.31 : x
2. Step 2: Convert to fraction form
   100.91/139.46 = 76.31/x
3. Step 3: Cross multiply
   100.91x = 139.46 × 76.31
4. Step 4: Simplify right side
   100.91x = 10,641.64
5. Step 5: Solve for x
   x = 10,641.64/100.91
6. Step 6: Final answer
   x = 105.45