Finding the Fourth Proportional to 1,385.91, 1,912.55 and 861.94

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.91 : 1,912.55 = 861.94 : x
2. Step 2: Convert to fraction form
   1,385.91/1,912.55 = 861.94/x
3. Step 3: Cross multiply
   1,385.91x = 1,912.55 × 861.94
4. Step 4: Simplify right side
   1,385.91x = 1,648,500.72
5. Step 5: Solve for x
   x = 1,648,500.72/1,385.91
6. Step 6: Final answer
   x = 1,189.47