Finding the Fourth Proportional to 1,021.78, 1,409.46 and 628.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,021.78 : 1,409.46 = 628.72 : x
2. Step 2: Convert to fraction form
   1,021.78/1,409.46 = 628.72/x
3. Step 3: Cross multiply
   1,021.78x = 1,409.46 × 628.72
4. Step 4: Simplify right side
   1,021.78x = 886,155.69
5. Step 5: Solve for x
   x = 886,155.69/1,021.78
6. Step 6: Final answer
   x = 867.27