Finding the Fourth Proportional to 72.79, 108.90 and 72.31

Step by Step Solution

1. Step 1: Write the proportion equation
   72.79 : 108.90 = 72.31 : x
2. Step 2: Convert to fraction form
   72.79/108.90 = 72.31/x
3. Step 3: Cross multiply
   72.79x = 108.90 × 72.31
4. Step 4: Simplify right side
   72.79x = 7,874.56
5. Step 5: Solve for x
   x = 7,874.56/72.79
6. Step 6: Final answer
   x = 108.18