Finding the Fourth Proportional to 1,390.38, 1,917.91 and 866.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.38 : 1,917.91 = 866.58 : x
2. Step 2: Convert to fraction form
   1,390.38/1,917.91 = 866.58/x
3. Step 3: Cross multiply
   1,390.38x = 1,917.91 × 866.58
4. Step 4: Simplify right side
   1,390.38x = 1,662,022.45
5. Step 5: Solve for x
   x = 1,662,022.45/1,390.38
6. Step 6: Final answer
   x = 1,195.37