Finding the Fourth Proportional to 1,039.30, 1,559.18 and 390.04

Step by Step Solution

1. Step 1: Write the proportion equation
   1,039.30 : 1,559.18 = 390.04 : x
2. Step 2: Convert to fraction form
   1,039.30/1,559.18 = 390.04/x
3. Step 3: Cross multiply
   1,039.30x = 1,559.18 × 390.04
4. Step 4: Simplify right side
   1,039.30x = 608,142.57
5. Step 5: Solve for x
   x = 608,142.57/1,039.30
6. Step 6: Final answer
   x = 585.15