Finding the Fourth Proportional to 85.58, 128.52 and 80.42

Step by Step Solution

1. Step 1: Write the proportion equation
   85.58 : 128.52 = 80.42 : x
2. Step 2: Convert to fraction form
   85.58/128.52 = 80.42/x
3. Step 3: Cross multiply
   85.58x = 128.52 × 80.42
4. Step 4: Simplify right side
   85.58x = 10,335.58
5. Step 5: Solve for x
   x = 10,335.58/85.58
6. Step 6: Final answer
   x = 120.77