Finding the Fourth Proportional to 1,039.76, 1,560.33 and 390.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,039.76 : 1,560.33 = 390.50 : x
2. Step 2: Convert to fraction form
   1,039.76/1,560.33 = 390.50/x
3. Step 3: Cross multiply
   1,039.76x = 1,560.33 × 390.50
4. Step 4: Simplify right side
   1,039.76x = 609,301.06
5. Step 5: Solve for x
   x = 609,301.06/1,039.76
6. Step 6: Final answer
   x = 586.00