Finding the Fourth Proportional to 105.72, 145.86 and 86.28

Step by Step Solution

1. Step 1: Write the proportion equation
   105.72 : 145.86 = 86.28 : x
2. Step 2: Convert to fraction form
   105.72/145.86 = 86.28/x
3. Step 3: Cross multiply
   105.72x = 145.86 × 86.28
4. Step 4: Simplify right side
   105.72x = 12,584.80
5. Step 5: Solve for x
   x = 12,584.80/105.72
6. Step 6: Final answer
   x = 119.04