Finding the Fourth Proportional to 1,399.69, 1,931.86 and 810.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.69 : 1,931.86 = 810.55 : x
2. Step 2: Convert to fraction form
   1,399.69/1,931.86 = 810.55/x
3. Step 3: Cross multiply
   1,399.69x = 1,931.86 × 810.55
4. Step 4: Simplify right side
   1,399.69x = 1,565,869.12
5. Step 5: Solve for x
   x = 1,565,869.12/1,399.69
6. Step 6: Final answer
   x = 1,118.73