Finding the Fourth Proportional to 3,978.92, 5,490.78 and 2,406.74

Step by Step Solution

1. Step 1: Write the proportion equation
   3,978.92 : 5,490.78 = 2,406.74 : x
2. Step 2: Convert to fraction form
   3,978.92/5,490.78 = 2,406.74/x
3. Step 3: Cross multiply
   3,978.92x = 5,490.78 × 2,406.74
4. Step 4: Simplify right side
   3,978.92x = 13,214,879.86
5. Step 5: Solve for x
   x = 13,214,879.86/3,978.92
6. Step 6: Final answer
   x = 3,321.22