Finding the Fourth Proportional to 1,061.78, 1,590.42 and 865.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,061.78 : 1,590.42 = 865.88 : x
2. Step 2: Convert to fraction form
   1,061.78/1,590.42 = 865.88/x
3. Step 3: Cross multiply
   1,061.78x = 1,590.42 × 865.88
4. Step 4: Simplify right side
   1,061.78x = 1,377,112.87
5. Step 5: Solve for x
   x = 1,377,112.87/1,061.78
6. Step 6: Final answer
   x = 1,296.99