Finding the Fourth Proportional to 2,139.52, 3,209.76 and 678.76

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.52 : 3,209.76 = 678.76 : x
2. Step 2: Convert to fraction form
   2,139.52/3,209.76 = 678.76/x
3. Step 3: Cross multiply
   2,139.52x = 3,209.76 × 678.76
4. Step 4: Simplify right side
   2,139.52x = 2,178,656.70
5. Step 5: Solve for x
   x = 2,178,656.70/2,139.52
6. Step 6: Final answer
   x = 1,018.29