Finding the Fourth Proportional to 1,399.57, 1,931.49 and 810.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.57 : 1,931.49 = 810.31 : x
2. Step 2: Convert to fraction form
   1,399.57/1,931.49 = 810.31/x
3. Step 3: Cross multiply
   1,399.57x = 1,931.49 × 810.31
4. Step 4: Simplify right side
   1,399.57x = 1,565,091.95
5. Step 5: Solve for x
   x = 1,565,091.95/1,399.57
6. Step 6: Final answer
   x = 1,118.27