Finding the Fourth Proportional to 1,390.40, 1,918.32 and 866.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.40 : 1,918.32 = 866.56 : x
2. Step 2: Convert to fraction form
   1,390.40/1,918.32 = 866.56/x
3. Step 3: Cross multiply
   1,390.40x = 1,918.32 × 866.56
4. Step 4: Simplify right side
   1,390.40x = 1,662,339.38
5. Step 5: Solve for x
   x = 1,662,339.38/1,390.40
6. Step 6: Final answer
   x = 1,195.58