Finding the Fourth Proportional to 1,399.08, 1,930.16 and 839.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.08 : 1,930.16 = 839.60 : x
2. Step 2: Convert to fraction form
   1,399.08/1,930.16 = 839.60/x
3. Step 3: Cross multiply
   1,399.08x = 1,930.16 × 839.60
4. Step 4: Simplify right side
   1,399.08x = 1,620,562.34
5. Step 5: Solve for x
   x = 1,620,562.34/1,399.08
6. Step 6: Final answer
   x = 1,158.31