Finding the Fourth Proportional to 85.98, 128.91 and 57.10

Step by Step Solution

1. Step 1: Write the proportion equation
   85.98 : 128.91 = 57.10 : x
2. Step 2: Convert to fraction form
   85.98/128.91 = 57.10/x
3. Step 3: Cross multiply
   85.98x = 128.91 × 57.10
4. Step 4: Simplify right side
   85.98x = 7,360.76
5. Step 5: Solve for x
   x = 7,360.76/85.98
6. Step 6: Final answer
   x = 85.61