Finding the Fourth Proportional to 1,399.07, 1,930.79 and 809.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.07 : 1,930.79 = 809.81 : x
2. Step 2: Convert to fraction form
   1,399.07/1,930.79 = 809.81/x
3. Step 3: Cross multiply
   1,399.07x = 1,930.79 × 809.81
4. Step 4: Simplify right side
   1,399.07x = 1,563,565.42
5. Step 5: Solve for x
   x = 1,563,565.42/1,399.07
6. Step 6: Final answer
   x = 1,117.58