Finding the Fourth Proportional to 1,442.78, 1,990.92 and 821.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,442.78 : 1,990.92 = 821.78 : x
2. Step 2: Convert to fraction form
   1,442.78/1,990.92 = 821.78/x
3. Step 3: Cross multiply
   1,442.78x = 1,990.92 × 821.78
4. Step 4: Simplify right side
   1,442.78x = 1,636,098.24
5. Step 5: Solve for x
   x = 1,636,098.24/1,442.78
6. Step 6: Final answer
   x = 1,133.99