Finding the Fourth Proportional to 92.78, 128.18 and 85.49

Step by Step Solution

1. Step 1: Write the proportion equation
   92.78 : 128.18 = 85.49 : x
2. Step 2: Convert to fraction form
   92.78/128.18 = 85.49/x
3. Step 3: Cross multiply
   92.78x = 128.18 × 85.49
4. Step 4: Simplify right side
   92.78x = 10,957.04
5. Step 5: Solve for x
   x = 10,957.04/92.78
6. Step 6: Final answer
   x = 118.10