Finding the Fourth Proportional to 1,005.54, 1,387.89 and 612.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.54 : 1,387.89 = 612.78 : x
2. Step 2: Convert to fraction form
   1,005.54/1,387.89 = 612.78/x
3. Step 3: Cross multiply
   1,005.54x = 1,387.89 × 612.78
4. Step 4: Simplify right side
   1,005.54x = 850,471.23
5. Step 5: Solve for x
   x = 850,471.23/1,005.54
6. Step 6: Final answer
   x = 845.79