Finding the Fourth Proportional to 1,391.48, 1,920.66 and 860.52

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.48 : 1,920.66 = 860.52 : x
2. Step 2: Convert to fraction form
   1,391.48/1,920.66 = 860.52/x
3. Step 3: Cross multiply
   1,391.48x = 1,920.66 × 860.52
4. Step 4: Simplify right side
   1,391.48x = 1,652,766.34
5. Step 5: Solve for x
   x = 1,652,766.34/1,391.48
6. Step 6: Final answer
   x = 1,187.78