Finding the Fourth Proportional to 3,978.12, 5,489.30 and 2,209.40

Step by Step Solution

1. Step 1: Write the proportion equation
   3,978.12 : 5,489.30 = 2,209.40 : x
2. Step 2: Convert to fraction form
   3,978.12/5,489.30 = 2,209.40/x
3. Step 3: Cross multiply
   3,978.12x = 5,489.30 × 2,209.40
4. Step 4: Simplify right side
   3,978.12x = 12,128,059.42
5. Step 5: Solve for x
   x = 12,128,059.42/3,978.12
6. Step 6: Final answer
   x = 3,048.69