Finding the Fourth Proportional to 1,391.20, 1,920.52 and 867.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.20 : 1,920.52 = 867.40 : x
2. Step 2: Convert to fraction form
   1,391.20/1,920.52 = 867.40/x
3. Step 3: Cross multiply
   1,391.20x = 1,920.52 × 867.40
4. Step 4: Simplify right side
   1,391.20x = 1,665,859.05
5. Step 5: Solve for x
   x = 1,665,859.05/1,391.20
6. Step 6: Final answer
   x = 1,197.43