Finding the Fourth Proportional to 1,290.05, 1,780.42 and 766.08

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.05 : 1,780.42 = 766.08 : x
2. Step 2: Convert to fraction form
   1,290.05/1,780.42 = 766.08/x
3. Step 3: Cross multiply
   1,290.05x = 1,780.42 × 766.08
4. Step 4: Simplify right side
   1,290.05x = 1,363,948.93
5. Step 5: Solve for x
   x = 1,363,948.93/1,290.05
6. Step 6: Final answer
   x = 1,057.28