Finding the Fourth Proportional to 1,310.61, 1,965.59 and 385.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,310.61 : 1,965.59 = 385.91 : x
2. Step 2: Convert to fraction form
   1,310.61/1,965.59 = 385.91/x
3. Step 3: Cross multiply
   1,310.61x = 1,965.59 × 385.91
4. Step 4: Simplify right side
   1,310.61x = 758,546.72
5. Step 5: Solve for x
   x = 758,546.72/1,310.61
6. Step 6: Final answer
   x = 578.78