Finding the Fourth Proportional to 1,391.09, 2,076.49 and 1,288.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.09 : 2,076.49 = 1,288.31 : x
2. Step 2: Convert to fraction form
   1,391.09/2,076.49 = 1,288.31/x
3. Step 3: Cross multiply
   1,391.09x = 2,076.49 × 1,288.31
4. Step 4: Simplify right side
   1,391.09x = 2,675,156.39
5. Step 5: Solve for x
   x = 2,675,156.39/1,391.09
6. Step 6: Final answer
   x = 1,923.06