Finding the Fourth Proportional to 85.50, 128.25 and 83.25

Step by Step Solution

1. Step 1: Write the proportion equation
   85.50 : 128.25 = 83.25 : x
2. Step 2: Convert to fraction form
   85.50/128.25 = 83.25/x
3. Step 3: Cross multiply
   85.50x = 128.25 × 83.25
4. Step 4: Simplify right side
   85.50x = 10,676.81
5. Step 5: Solve for x
   x = 10,676.81/85.50
6. Step 6: Final answer
   x = 124.88