Finding the Fourth Proportional to 105.59, 158.09 and 86.28

Step by Step Solution

1. Step 1: Write the proportion equation
   105.59 : 158.09 = 86.28 : x
2. Step 2: Convert to fraction form
   105.59/158.09 = 86.28/x
3. Step 3: Cross multiply
   105.59x = 158.09 × 86.28
4. Step 4: Simplify right side
   105.59x = 13,640.01
5. Step 5: Solve for x
   x = 13,640.01/105.59
6. Step 6: Final answer
   x = 129.18