Finding the Fourth Proportional to 2,172.57, 3,257.31 and 939.30

Step by Step Solution

1. Step 1: Write the proportion equation
   2,172.57 : 3,257.31 = 939.30 : x
2. Step 2: Convert to fraction form
   2,172.57/3,257.31 = 939.30/x
3. Step 3: Cross multiply
   2,172.57x = 3,257.31 × 939.30
4. Step 4: Simplify right side
   2,172.57x = 3,059,586.59
5. Step 5: Solve for x
   x = 3,059,586.59/2,172.57
6. Step 6: Final answer
   x = 1,408.28