Finding the Fourth Proportional to 1,143.78, 1,578.31 and 646.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,143.78 : 1,578.31 = 646.30 : x
2. Step 2: Convert to fraction form
   1,143.78/1,578.31 = 646.30/x
3. Step 3: Cross multiply
   1,143.78x = 1,578.31 × 646.30
4. Step 4: Simplify right side
   1,143.78x = 1,020,061.75
5. Step 5: Solve for x
   x = 1,020,061.75/1,143.78
6. Step 6: Final answer
   x = 891.83