Finding the Fourth Proportional to 1,290.27, 1,780.81 and 766.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.27 : 1,780.81 = 766.61 : x
2. Step 2: Convert to fraction form
   1,290.27/1,780.81 = 766.61/x
3. Step 3: Cross multiply
   1,290.27x = 1,780.81 × 766.61
4. Step 4: Simplify right side
   1,290.27x = 1,365,175.93
5. Step 5: Solve for x
   x = 1,365,175.93/1,290.27
6. Step 6: Final answer
   x = 1,058.05