Finding the Fourth Proportional to 1,078.78, 1,618.83 and 429.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.78 : 1,618.83 = 429.57 : x
2. Step 2: Convert to fraction form
   1,078.78/1,618.83 = 429.57/x
3. Step 3: Cross multiply
   1,078.78x = 1,618.83 × 429.57
4. Step 4: Simplify right side
   1,078.78x = 695,400.80
5. Step 5: Solve for x
   x = 695,400.80/1,078.78
6. Step 6: Final answer
   x = 644.62