Finding the Fourth Proportional to 1,399.88, 1,931.64 and 810.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.88 : 1,931.64 = 810.20 : x
2. Step 2: Convert to fraction form
   1,399.88/1,931.64 = 810.20/x
3. Step 3: Cross multiply
   1,399.88x = 1,931.64 × 810.20
4. Step 4: Simplify right side
   1,399.88x = 1,565,014.73
5. Step 5: Solve for x
   x = 1,565,014.73/1,399.88
6. Step 6: Final answer
   x = 1,117.96