Finding the Fourth Proportional to 3,978.78, 5,492.25 and 2,859.90

Step by Step Solution

1. Step 1: Write the proportion equation
   3,978.78 : 5,492.25 = 2,859.90 : x
2. Step 2: Convert to fraction form
   3,978.78/5,492.25 = 2,859.90/x
3. Step 3: Cross multiply
   3,978.78x = 5,492.25 × 2,859.90
4. Step 4: Simplify right side
   3,978.78x = 15,707,285.78
5. Step 5: Solve for x
   x = 15,707,285.78/3,978.78
6. Step 6: Final answer
   x = 3,947.76