Finding the Fourth Proportional to 86.02, 128.94 and 31.89

Step by Step Solution

1. Step 1: Write the proportion equation
   86.02 : 128.94 = 31.89 : x
2. Step 2: Convert to fraction form
   86.02/128.94 = 31.89/x
3. Step 3: Cross multiply
   86.02x = 128.94 × 31.89
4. Step 4: Simplify right side
   86.02x = 4,111.90
5. Step 5: Solve for x
   x = 4,111.90/86.02
6. Step 6: Final answer
   x = 47.80