Finding the Fourth Proportional to 2,616.45, 3,923.83 and 861.05

Step by Step Solution

1. Step 1: Write the proportion equation
   2,616.45 : 3,923.83 = 861.05 : x
2. Step 2: Convert to fraction form
   2,616.45/3,923.83 = 861.05/x
3. Step 3: Cross multiply
   2,616.45x = 3,923.83 × 861.05
4. Step 4: Simplify right side
   2,616.45x = 3,378,594.20
5. Step 5: Solve for x
   x = 3,378,594.20/2,616.45
6. Step 6: Final answer
   x = 1,291.29