Finding the Fourth Proportional to 85.43, 128.18 and 31.37

Step by Step Solution

1. Step 1: Write the proportion equation
   85.43 : 128.18 = 31.37 : x
2. Step 2: Convert to fraction form
   85.43/128.18 = 31.37/x
3. Step 3: Cross multiply
   85.43x = 128.18 × 31.37
4. Step 4: Simplify right side
   85.43x = 4,020.21
5. Step 5: Solve for x
   x = 4,020.21/85.43
6. Step 6: Final answer
   x = 47.06