Finding the Fourth Proportional to 1,391.72, 1,920.66 and 802.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.72 : 1,920.66 = 802.28 : x
2. Step 2: Convert to fraction form
   1,391.72/1,920.66 = 802.28/x
3. Step 3: Cross multiply
   1,391.72x = 1,920.66 × 802.28
4. Step 4: Simplify right side
   1,391.72x = 1,540,907.10
5. Step 5: Solve for x
   x = 1,540,907.10/1,391.72
6. Step 6: Final answer
   x = 1,107.20