Finding the Fourth Proportional to 2,165.15, 2,986.72 and 1,280.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,165.15 : 2,986.72 = 1,280.78 : x
2. Step 2: Convert to fraction form
   2,165.15/2,986.72 = 1,280.78/x
3. Step 3: Cross multiply
   2,165.15x = 2,986.72 × 1,280.78
4. Step 4: Simplify right side
   2,165.15x = 3,825,331.24
5. Step 5: Solve for x
   x = 3,825,331.24/2,165.15
6. Step 6: Final answer
   x = 1,766.77