Finding the Fourth Proportional to 1,209.69, 1,669.50 and 685.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.69 : 1,669.50 = 685.80 : x
2. Step 2: Convert to fraction form
   1,209.69/1,669.50 = 685.80/x
3. Step 3: Cross multiply
   1,209.69x = 1,669.50 × 685.80
4. Step 4: Simplify right side
   1,209.69x = 1,144,943.10
5. Step 5: Solve for x
   x = 1,144,943.10/1,209.69
6. Step 6: Final answer
   x = 946.48