Finding the Fourth Proportional to 1,389.64, 1,918.52 and 866.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.64 : 1,918.52 = 866.40 : x
2. Step 2: Convert to fraction form
   1,389.64/1,918.52 = 866.40/x
3. Step 3: Cross multiply
   1,389.64x = 1,918.52 × 866.40
4. Step 4: Simplify right side
   1,389.64x = 1,662,205.73
5. Step 5: Solve for x
   x = 1,662,205.73/1,389.64
6. Step 6: Final answer
   x = 1,196.14