Finding the Fourth Proportional to 1,390.58, 1,908.78 and 1,229.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.58 : 1,908.78 = 1,229.69 : x
2. Step 2: Convert to fraction form
   1,390.58/1,908.78 = 1,229.69/x
3. Step 3: Cross multiply
   1,390.58x = 1,908.78 × 1,229.69
4. Step 4: Simplify right side
   1,390.58x = 2,347,205.29
5. Step 5: Solve for x
   x = 2,347,205.29/1,390.58
6. Step 6: Final answer
   x = 1,687.93