Finding the Fourth Proportional to 1,209.69, 1,669.41 and 685.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.69 : 1,669.41 = 685.76 : x
2. Step 2: Convert to fraction form
   1,209.69/1,669.41 = 685.76/x
3. Step 3: Cross multiply
   1,209.69x = 1,669.41 × 685.76
4. Step 4: Simplify right side
   1,209.69x = 1,144,802.83
5. Step 5: Solve for x
   x = 1,144,802.83/1,209.69
6. Step 6: Final answer
   x = 946.36