Finding the Fourth Proportional to 2,592.78, 3,889.38 and 813.72

Step by Step Solution

1. Step 1: Write the proportion equation
   2,592.78 : 3,889.38 = 813.72 : x
2. Step 2: Convert to fraction form
   2,592.78/3,889.38 = 813.72/x
3. Step 3: Cross multiply
   2,592.78x = 3,889.38 × 813.72
4. Step 4: Simplify right side
   2,592.78x = 3,164,866.29
5. Step 5: Solve for x
   x = 3,164,866.29/2,592.78
6. Step 6: Final answer
   x = 1,220.65