Finding the Fourth Proportional to 85.38, 128.25 and 83.10

Step by Step Solution

1. Step 1: Write the proportion equation
   85.38 : 128.25 = 83.10 : x
2. Step 2: Convert to fraction form
   85.38/128.25 = 83.10/x
3. Step 3: Cross multiply
   85.38x = 128.25 × 83.10
4. Step 4: Simplify right side
   85.38x = 10,657.58
5. Step 5: Solve for x
   x = 10,657.58/85.38
6. Step 6: Final answer
   x = 124.83