Finding the Fourth Proportional to 2,139.68, 3,208.56 and 678.56

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.68 : 3,208.56 = 678.56 : x
2. Step 2: Convert to fraction form
   2,139.68/3,208.56 = 678.56/x
3. Step 3: Cross multiply
   2,139.68x = 3,208.56 × 678.56
4. Step 4: Simplify right side
   2,139.68x = 2,177,200.47
5. Step 5: Solve for x
   x = 2,177,200.47/2,139.68
6. Step 6: Final answer
   x = 1,017.54