Finding the Fourth Proportional to 1,238.69, 1,709.47 and 818.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,238.69 : 1,709.47 = 818.30 : x
2. Step 2: Convert to fraction form
   1,238.69/1,709.47 = 818.30/x
3. Step 3: Cross multiply
   1,238.69x = 1,709.47 × 818.30
4. Step 4: Simplify right side
   1,238.69x = 1,398,864.60
5. Step 5: Solve for x
   x = 1,398,864.60/1,238.69
6. Step 6: Final answer
   x = 1,129.31