Finding the Fourth Proportional to 1,209.89, 1,669.61 and 678.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.89 : 1,669.61 = 678.79 : x
2. Step 2: Convert to fraction form
   1,209.89/1,669.61 = 678.79/x
3. Step 3: Cross multiply
   1,209.89x = 1,669.61 × 678.79
4. Step 4: Simplify right side
   1,209.89x = 1,133,318.36
5. Step 5: Solve for x
   x = 1,133,318.36/1,209.89
6. Step 6: Final answer
   x = 936.71