Finding the Fourth Proportional to 3,900.15, 5,383.98 and 2,485.78

Step by Step Solution

1. Step 1: Write the proportion equation
   3,900.15 : 5,383.98 = 2,485.78 : x
2. Step 2: Convert to fraction form
   3,900.15/5,383.98 = 2,485.78/x
3. Step 3: Cross multiply
   3,900.15x = 5,383.98 × 2,485.78
4. Step 4: Simplify right side
   3,900.15x = 13,383,389.80
5. Step 5: Solve for x
   x = 13,383,389.80/3,900.15
6. Step 6: Final answer
   x = 3,431.51