Finding the Fourth Proportional to 1,391.64, 1,921.32 and 868.38

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.64 : 1,921.32 = 868.38 : x
2. Step 2: Convert to fraction form
   1,391.64/1,921.32 = 868.38/x
3. Step 3: Cross multiply
   1,391.64x = 1,921.32 × 868.38
4. Step 4: Simplify right side
   1,391.64x = 1,668,435.86
5. Step 5: Solve for x
   x = 1,668,435.86/1,391.64
6. Step 6: Final answer
   x = 1,198.90