Finding the Fourth Proportional to 105.48, 158.56 and 85.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.48 : 158.56 = 85.42 : x
2. Step 2: Convert to fraction form
   105.48/158.56 = 85.42/x
3. Step 3: Cross multiply
   105.48x = 158.56 × 85.42
4. Step 4: Simplify right side
   105.48x = 13,544.20
5. Step 5: Solve for x
   x = 13,544.20/105.48
6. Step 6: Final answer
   x = 128.41