Finding the Fourth Proportional to 1,390.72, 1,919.52 and 866.44

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.72 : 1,919.52 = 866.44 : x
2. Step 2: Convert to fraction form
   1,390.72/1,919.52 = 866.44/x
3. Step 3: Cross multiply
   1,390.72x = 1,919.52 × 866.44
4. Step 4: Simplify right side
   1,390.72x = 1,663,148.91
5. Step 5: Solve for x
   x = 1,663,148.91/1,390.72
6. Step 6: Final answer
   x = 1,195.89