Finding the Fourth Proportional to 1,209.67, 1,669.33 and 678.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.67 : 1,669.33 = 678.55 : x
2. Step 2: Convert to fraction form
   1,209.67/1,669.33 = 678.55/x
3. Step 3: Cross multiply
   1,209.67x = 1,669.33 × 678.55
4. Step 4: Simplify right side
   1,209.67x = 1,132,724.65
5. Step 5: Solve for x
   x = 1,132,724.65/1,209.67
6. Step 6: Final answer
   x = 936.39