Finding the Fourth Proportional to 105.31, 145.42 and 86.86

Step by Step Solution

1. Step 1: Write the proportion equation
   105.31 : 145.42 = 86.86 : x
2. Step 2: Convert to fraction form
   105.31/145.42 = 86.86/x
3. Step 3: Cross multiply
   105.31x = 145.42 × 86.86
4. Step 4: Simplify right side
   105.31x = 12,630.60
5. Step 5: Solve for x
   x = 12,630.60/105.31
6. Step 6: Final answer
   x = 119.94