Finding the Fourth Proportional to 86.00, 128.22 and 85.10

Step by Step Solution

1. Step 1: Write the proportion equation
   86.00 : 128.22 = 85.10 : x
2. Step 2: Convert to fraction form
   86.00/128.22 = 85.10/x
3. Step 3: Cross multiply
   86.00x = 128.22 × 85.10
4. Step 4: Simplify right side
   86.00x = 10,910.56
5. Step 5: Solve for x
   x = 10,910.56/86.00
6. Step 6: Final answer
   x = 126.87