Finding the Fourth Proportional to 85.54, 128.21 and 78.02

Step by Step Solution

1. Step 1: Write the proportion equation
   85.54 : 128.21 = 78.02 : x
2. Step 2: Convert to fraction form
   85.54/128.21 = 78.02/x
3. Step 3: Cross multiply
   85.54x = 128.21 × 78.02
4. Step 4: Simplify right side
   85.54x = 10,002.30
5. Step 5: Solve for x
   x = 10,002.30/85.54
6. Step 6: Final answer
   x = 116.94