Finding the Fourth Proportional to 105.18, 145.34 and 86.72

Step by Step Solution

1. Step 1: Write the proportion equation
   105.18 : 145.34 = 86.72 : x
2. Step 2: Convert to fraction form
   105.18/145.34 = 86.72/x
3. Step 3: Cross multiply
   105.18x = 145.34 × 86.72
4. Step 4: Simplify right side
   105.18x = 12,603.88
5. Step 5: Solve for x
   x = 12,603.88/105.18
6. Step 6: Final answer
   x = 119.83