Finding the Fourth Proportional to 2,139.52, 3,209.52 and 678.40

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.52 : 3,209.52 = 678.40 : x
2. Step 2: Convert to fraction form
   2,139.52/3,209.52 = 678.40/x
3. Step 3: Cross multiply
   2,139.52x = 3,209.52 × 678.40
4. Step 4: Simplify right side
   2,139.52x = 2,177,338.37
5. Step 5: Solve for x
   x = 2,177,338.37/2,139.52
6. Step 6: Final answer
   x = 1,017.68