Finding the Fourth Proportional to 1,209.30, 1,668.82 and 685.35

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.30 : 1,668.82 = 685.35 : x
2. Step 2: Convert to fraction form
   1,209.30/1,668.82 = 685.35/x
3. Step 3: Cross multiply
   1,209.30x = 1,668.82 × 685.35
4. Step 4: Simplify right side
   1,209.30x = 1,143,725.79
5. Step 5: Solve for x
   x = 1,143,725.79/1,209.30
6. Step 6: Final answer
   x = 945.78