Finding the Fourth Proportional to 85.76, 128.71 and 31.67

Step by Step Solution

1. Step 1: Write the proportion equation
   85.76 : 128.71 = 31.67 : x
2. Step 2: Convert to fraction form
   85.76/128.71 = 31.67/x
3. Step 3: Cross multiply
   85.76x = 128.71 × 31.67
4. Step 4: Simplify right side
   85.76x = 4,076.61
5. Step 5: Solve for x
   x = 4,076.61/85.76
6. Step 6: Final answer
   x = 47.53