Finding the Fourth Proportional to 6,258.40, 8,639.40 and 3,990.72

Step by Step Solution

1. Step 1: Write the proportion equation
   6,258.40 : 8,639.40 = 3,990.72 : x
2. Step 2: Convert to fraction form
   6,258.40/8,639.40 = 3,990.72/x
3. Step 3: Cross multiply
   6,258.40x = 8,639.40 × 3,990.72
4. Step 4: Simplify right side
   6,258.40x = 34,477,426.37
5. Step 5: Solve for x
   x = 34,477,426.37/6,258.40
6. Step 6: Final answer
   x = 5,508.98