Finding the Fourth Proportional to 1,391.71, 1,919.82 and 860.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.71 : 1,919.82 = 860.89 : x
2. Step 2: Convert to fraction form
   1,391.71/1,919.82 = 860.89/x
3. Step 3: Cross multiply
   1,391.71x = 1,919.82 × 860.89
4. Step 4: Simplify right side
   1,391.71x = 1,652,753.84
5. Step 5: Solve for x
   x = 1,652,753.84/1,391.71
6. Step 6: Final answer
   x = 1,187.57