Finding the Fourth Proportional to 2,139.57, 3,210.03 and 678.74

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.57 : 3,210.03 = 678.74 : x
2. Step 2: Convert to fraction form
   2,139.57/3,210.03 = 678.74/x
3. Step 3: Cross multiply
   2,139.57x = 3,210.03 × 678.74
4. Step 4: Simplify right side
   2,139.57x = 2,178,759.71
5. Step 5: Solve for x
   x = 2,178,759.71/2,139.57
6. Step 6: Final answer
   x = 1,018.32