Finding the Fourth Proportional to 1,390.21, 1,908.27 and 1,229.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.21 : 1,908.27 = 1,229.31 : x
2. Step 2: Convert to fraction form
   1,390.21/1,908.27 = 1,229.31/x
3. Step 3: Cross multiply
   1,390.21x = 1,908.27 × 1,229.31
4. Step 4: Simplify right side
   1,390.21x = 2,345,857.94
5. Step 5: Solve for x
   x = 2,345,857.94/1,390.21
6. Step 6: Final answer
   x = 1,687.42