Finding the Fourth Proportional to 1,391.90, 1,920.78 and 802.49

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.90 : 1,920.78 = 802.49 : x
2. Step 2: Convert to fraction form
   1,391.90/1,920.78 = 802.49/x
3. Step 3: Cross multiply
   1,391.90x = 1,920.78 × 802.49
4. Step 4: Simplify right side
   1,391.90x = 1,541,397.14
5. Step 5: Solve for x
   x = 1,541,397.14/1,391.90
6. Step 6: Final answer
   x = 1,107.41