Finding the Fourth Proportional to 1,399.86, 1,931.98 and 810.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.86 : 1,931.98 = 810.40 : x
2. Step 2: Convert to fraction form
   1,399.86/1,931.98 = 810.40/x
3. Step 3: Cross multiply
   1,399.86x = 1,931.98 × 810.40
4. Step 4: Simplify right side
   1,399.86x = 1,565,667.17
5. Step 5: Solve for x
   x = 1,565,667.17/1,399.86
6. Step 6: Final answer
   x = 1,118.45