Finding the Fourth Proportional to 1,421.27, 1,960.72 and 831.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.27 : 1,960.72 = 831.55 : x
2. Step 2: Convert to fraction form
   1,421.27/1,960.72 = 831.55/x
3. Step 3: Cross multiply
   1,421.27x = 1,960.72 × 831.55
4. Step 4: Simplify right side
   1,421.27x = 1,630,436.72
5. Step 5: Solve for x
   x = 1,630,436.72/1,421.27
6. Step 6: Final answer
   x = 1,147.17