Finding the Fourth Proportional to 1,392.69, 1,921.40 and 825.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,392.69 : 1,921.40 = 825.40 : x
2. Step 2: Convert to fraction form
   1,392.69/1,921.40 = 825.40/x
3. Step 3: Cross multiply
   1,392.69x = 1,921.40 × 825.40
4. Step 4: Simplify right side
   1,392.69x = 1,585,924.93
5. Step 5: Solve for x
   x = 1,585,924.93/1,392.69
6. Step 6: Final answer
   x = 1,138.75