Finding the Fourth Proportional to 85.97, 128.90 and 42.59

Step by Step Solution

1. Step 1: Write the proportion equation
   85.97 : 128.90 = 42.59 : x
2. Step 2: Convert to fraction form
   85.97/128.90 = 42.59/x
3. Step 3: Cross multiply
   85.97x = 128.90 × 42.59
4. Step 4: Simplify right side
   85.97x = 5,489.21
5. Step 5: Solve for x
   x = 5,489.21/85.97
6. Step 6: Final answer
   x = 63.85