Finding the Fourth Proportional to 99.91, 138.07 and 75.31

Step by Step Solution

1. Step 1: Write the proportion equation
   99.91 : 138.07 = 75.31 : x
2. Step 2: Convert to fraction form
   99.91/138.07 = 75.31/x
3. Step 3: Cross multiply
   99.91x = 138.07 × 75.31
4. Step 4: Simplify right side
   99.91x = 10,397.69
5. Step 5: Solve for x
   x = 10,397.69/99.91
6. Step 6: Final answer
   x = 104.07