Finding the Fourth Proportional to 2,139.57, 3,209.67 and 678.42

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.57 : 3,209.67 = 678.42 : x
2. Step 2: Convert to fraction form
   2,139.57/3,209.67 = 678.42/x
3. Step 3: Cross multiply
   2,139.57x = 3,209.67 × 678.42
4. Step 4: Simplify right side
   2,139.57x = 2,177,504.32
5. Step 5: Solve for x
   x = 2,177,504.32/2,139.57
6. Step 6: Final answer
   x = 1,017.73