Finding the Fourth Proportional to 1,380.85, 2,072.31 and 861.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.85 : 2,072.31 = 861.61 : x
2. Step 2: Convert to fraction form
   1,380.85/2,072.31 = 861.61/x
3. Step 3: Cross multiply
   1,380.85x = 2,072.31 × 861.61
4. Step 4: Simplify right side
   1,380.85x = 1,785,523.02
5. Step 5: Solve for x
   x = 1,785,523.02/1,380.85
6. Step 6: Final answer
   x = 1,293.06