Finding the Fourth Proportional to 1,039.59, 1,559.69 and 390.38

Step by Step Solution

1. Step 1: Write the proportion equation
   1,039.59 : 1,559.69 = 390.38 : x
2. Step 2: Convert to fraction form
   1,039.59/1,559.69 = 390.38/x
3. Step 3: Cross multiply
   1,039.59x = 1,559.69 × 390.38
4. Step 4: Simplify right side
   1,039.59x = 608,863.50
5. Step 5: Solve for x
   x = 608,863.50/1,039.59
6. Step 6: Final answer
   x = 585.68