Finding the Fourth Proportional to 85.58, 128.54 and 83.30

Step by Step Solution

1. Step 1: Write the proportion equation
   85.58 : 128.54 = 83.30 : x
2. Step 2: Convert to fraction form
   85.58/128.54 = 83.30/x
3. Step 3: Cross multiply
   85.58x = 128.54 × 83.30
4. Step 4: Simplify right side
   85.58x = 10,707.43
5. Step 5: Solve for x
   x = 10,707.43/85.58
6. Step 6: Final answer
   x = 125.12