Finding the Fourth Proportional to 1,399.21, 1,930.57 and 809.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.21 : 1,930.57 = 809.71 : x
2. Step 2: Convert to fraction form
   1,399.21/1,930.57 = 809.71/x
3. Step 3: Cross multiply
   1,399.21x = 1,930.57 × 809.71
4. Step 4: Simplify right side
   1,399.21x = 1,563,201.83
5. Step 5: Solve for x
   x = 1,563,201.83/1,399.21
6. Step 6: Final answer
   x = 1,117.20