Finding the Fourth Proportional to 1,399.38, 1,930.94 and 809.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.38 : 1,930.94 = 809.80 : x
2. Step 2: Convert to fraction form
   1,399.38/1,930.94 = 809.80/x
3. Step 3: Cross multiply
   1,399.38x = 1,930.94 × 809.80
4. Step 4: Simplify right side
   1,399.38x = 1,563,669.37
5. Step 5: Solve for x
   x = 1,563,669.37/1,399.38
6. Step 6: Final answer
   x = 1,117.40