Finding the Fourth Proportional to 1,012.78, 1,396.20 and 717.94

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.78 : 1,396.20 = 717.94 : x
2. Step 2: Convert to fraction form
   1,012.78/1,396.20 = 717.94/x
3. Step 3: Cross multiply
   1,012.78x = 1,396.20 × 717.94
4. Step 4: Simplify right side
   1,012.78x = 1,002,387.83
5. Step 5: Solve for x
   x = 1,002,387.83/1,012.78
6. Step 6: Final answer
   x = 989.74