Finding the Fourth Proportional to 85.91, 128.88 and 31.82

Step by Step Solution

1. Step 1: Write the proportion equation
   85.91 : 128.88 = 31.82 : x
2. Step 2: Convert to fraction form
   85.91/128.88 = 31.82/x
3. Step 3: Cross multiply
   85.91x = 128.88 × 31.82
4. Step 4: Simplify right side
   85.91x = 4,100.32
5. Step 5: Solve for x
   x = 4,100.32/85.91
6. Step 6: Final answer
   x = 47.73