Finding the Fourth Proportional to 1,385.70, 1,912.17 and 861.63

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.70 : 1,912.17 = 861.63 : x
2. Step 2: Convert to fraction form
   1,385.70/1,912.17 = 861.63/x
3. Step 3: Cross multiply
   1,385.70x = 1,912.17 × 861.63
4. Step 4: Simplify right side
   1,385.70x = 1,647,583.04
5. Step 5: Solve for x
   x = 1,647,583.04/1,385.70
6. Step 6: Final answer
   x = 1,188.99