Finding the Fourth Proportional to 2,139.56, 3,209.46 and 678.61

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.56 : 3,209.46 = 678.61 : x
2. Step 2: Convert to fraction form
   2,139.56/3,209.46 = 678.61/x
3. Step 3: Cross multiply
   2,139.56x = 3,209.46 × 678.61
4. Step 4: Simplify right side
   2,139.56x = 2,177,952.21
5. Step 5: Solve for x
   x = 2,177,952.21/2,139.56
6. Step 6: Final answer
   x = 1,017.95