Finding the Fourth Proportional to 1,392.10, 1,921.20 and 802.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,392.10 : 1,921.20 = 802.72 : x
2. Step 2: Convert to fraction form
   1,392.10/1,921.20 = 802.72/x
3. Step 3: Cross multiply
   1,392.10x = 1,921.20 × 802.72
4. Step 4: Simplify right side
   1,392.10x = 1,542,185.66
5. Step 5: Solve for x
   x = 1,542,185.66/1,392.10
6. Step 6: Final answer
   x = 1,107.81