Finding the Fourth Proportional to 1,391.38, 1,920.04 and 831.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.38 : 1,920.04 = 831.90 : x
2. Step 2: Convert to fraction form
   1,391.38/1,920.04 = 831.90/x
3. Step 3: Cross multiply
   1,391.38x = 1,920.04 × 831.90
4. Step 4: Simplify right side
   1,391.38x = 1,597,281.28
5. Step 5: Solve for x
   x = 1,597,281.28/1,391.38
6. Step 6: Final answer
   x = 1,147.98