Finding the Fourth Proportional to 1,389.06, 1,917.72 and 865.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.06 : 1,917.72 = 865.80 : x
2. Step 2: Convert to fraction form
   1,389.06/1,917.72 = 865.80/x
3. Step 3: Cross multiply
   1,389.06x = 1,917.72 × 865.80
4. Step 4: Simplify right side
   1,389.06x = 1,660,361.98
5. Step 5: Solve for x
   x = 1,660,361.98/1,389.06
6. Step 6: Final answer
   x = 1,195.31