Finding the Fourth Proportional to 1,399.31, 1,930.89 and 839.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.31 : 1,930.89 = 839.81 : x
2. Step 2: Convert to fraction form
   1,399.31/1,930.89 = 839.81/x
3. Step 3: Cross multiply
   1,399.31x = 1,930.89 × 839.81
4. Step 4: Simplify right side
   1,399.31x = 1,621,571.08
5. Step 5: Solve for x
   x = 1,621,571.08/1,399.31
6. Step 6: Final answer
   x = 1,158.84