Finding the Fourth Proportional to 1,290.78, 1,781.31 and 759.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.78 : 1,781.31 = 759.69 : x
2. Step 2: Convert to fraction form
   1,290.78/1,781.31 = 759.69/x
3. Step 3: Cross multiply
   1,290.78x = 1,781.31 × 759.69
4. Step 4: Simplify right side
   1,290.78x = 1,353,243.39
5. Step 5: Solve for x
   x = 1,353,243.39/1,290.78
6. Step 6: Final answer
   x = 1,048.39