Finding the Fourth Proportional to 1,039.89, 1,560.10 and 390.63

Step by Step Solution

1. Step 1: Write the proportion equation
   1,039.89 : 1,560.10 = 390.63 : x
2. Step 2: Convert to fraction form
   1,039.89/1,560.10 = 390.63/x
3. Step 3: Cross multiply
   1,039.89x = 1,560.10 × 390.63
4. Step 4: Simplify right side
   1,039.89x = 609,421.86
5. Step 5: Solve for x
   x = 609,421.86/1,039.89
6. Step 6: Final answer
   x = 586.04