Finding the Fourth Proportional to 1,020.89, 1,408.98 and 578.70

Step by Step Solution

1. Step 1: Write the proportion equation
   1,020.89 : 1,408.98 = 578.70 : x
2. Step 2: Convert to fraction form
   1,020.89/1,408.98 = 578.70/x
3. Step 3: Cross multiply
   1,020.89x = 1,408.98 × 578.70
4. Step 4: Simplify right side
   1,020.89x = 815,373.61
5. Step 5: Solve for x
   x = 815,373.61/1,020.89
6. Step 6: Final answer
   x = 798.69