Finding the Fourth Proportional to 1,038.78, 1,433.28 and 789.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,038.78 : 1,433.28 = 789.72 : x
2. Step 2: Convert to fraction form
   1,038.78/1,433.28 = 789.72/x
3. Step 3: Cross multiply
   1,038.78x = 1,433.28 × 789.72
4. Step 4: Simplify right side
   1,038.78x = 1,131,889.88
5. Step 5: Solve for x
   x = 1,131,889.88/1,038.78
6. Step 6: Final answer
   x = 1,089.63