Finding the Fourth Proportional to 2,659.94, 3,990.29 and 810.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,659.94 : 3,990.29 = 810.78 : x
2. Step 2: Convert to fraction form
   2,659.94/3,990.29 = 810.78/x
3. Step 3: Cross multiply
   2,659.94x = 3,990.29 × 810.78
4. Step 4: Simplify right side
   2,659.94x = 3,235,264.26
5. Step 5: Solve for x
   x = 3,235,264.26/2,659.94
6. Step 6: Final answer
   x = 1,216.29