Finding the Fourth Proportional to 1,398.57, 1,929.87 and 809.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.57 : 1,929.87 = 809.31 : x
2. Step 2: Convert to fraction form
   1,398.57/1,929.87 = 809.31/x
3. Step 3: Cross multiply
   1,398.57x = 1,929.87 × 809.31
4. Step 4: Simplify right side
   1,398.57x = 1,561,863.09
5. Step 5: Solve for x
   x = 1,561,863.09/1,398.57
6. Step 6: Final answer
   x = 1,116.76