Finding the Fourth Proportional to 86.31, 129.31 and 45.72

Step by Step Solution

1. Step 1: Write the proportion equation
   86.31 : 129.31 = 45.72 : x
2. Step 2: Convert to fraction form
   86.31/129.31 = 45.72/x
3. Step 3: Cross multiply
   86.31x = 129.31 × 45.72
4. Step 4: Simplify right side
   86.31x = 5,911.94
5. Step 5: Solve for x
   x = 5,911.94/86.31
6. Step 6: Final answer
   x = 68.50