Finding the Fourth Proportional to 105.86, 158.79 and 85.47

Step by Step Solution

1. Step 1: Write the proportion equation
   105.86 : 158.79 = 85.47 : x
2. Step 2: Convert to fraction form
   105.86/158.79 = 85.47/x
3. Step 3: Cross multiply
   105.86x = 158.79 × 85.47
4. Step 4: Simplify right side
   105.86x = 13,571.78
5. Step 5: Solve for x
   x = 13,571.78/105.86
6. Step 6: Final answer
   x = 128.21