Finding the Fourth Proportional to 3,953.78, 5,456.25 and 2,161.31

Step by Step Solution

1. Step 1: Write the proportion equation
   3,953.78 : 5,456.25 = 2,161.31 : x
2. Step 2: Convert to fraction form
   3,953.78/5,456.25 = 2,161.31/x
3. Step 3: Cross multiply
   3,953.78x = 5,456.25 × 2,161.31
4. Step 4: Simplify right side
   3,953.78x = 11,792,647.69
5. Step 5: Solve for x
   x = 11,792,647.69/3,953.78
6. Step 6: Final answer
   x = 2,982.63