Finding the Fourth Proportional to 1,224.86, 1,689.36 and 831.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,224.86 : 1,689.36 = 831.20 : x
2. Step 2: Convert to fraction form
   1,224.86/1,689.36 = 831.20/x
3. Step 3: Cross multiply
   1,224.86x = 1,689.36 × 831.20
4. Step 4: Simplify right side
   1,224.86x = 1,404,196.03
5. Step 5: Solve for x
   x = 1,404,196.03/1,224.86
6. Step 6: Final answer
   x = 1,146.41