Finding the Fourth Proportional to 2,911.28, 4,367.60 and 831.31

Step by Step Solution

1. Step 1: Write the proportion equation
   2,911.28 : 4,367.60 = 831.31 : x
2. Step 2: Convert to fraction form
   2,911.28/4,367.60 = 831.31/x
3. Step 3: Cross multiply
   2,911.28x = 4,367.60 × 831.31
4. Step 4: Simplify right side
   2,911.28x = 3,630,830.86
5. Step 5: Solve for x
   x = 3,630,830.86/2,911.28
6. Step 6: Final answer
   x = 1,247.16