Finding the Fourth Proportional to 1,443.78, 1,992.43 and 780.64

Step by Step Solution

1. Step 1: Write the proportion equation
   1,443.78 : 1,992.43 = 780.64 : x
2. Step 2: Convert to fraction form
   1,443.78/1,992.43 = 780.64/x
3. Step 3: Cross multiply
   1,443.78x = 1,992.43 × 780.64
4. Step 4: Simplify right side
   1,443.78x = 1,555,371.09
5. Step 5: Solve for x
   x = 1,555,371.09/1,443.78
6. Step 6: Final answer
   x = 1,077.29