Finding the Fourth Proportional to 1,209.79, 1,669.89 and 686.17

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.79 : 1,669.89 = 686.17 : x
2. Step 2: Convert to fraction form
   1,209.79/1,669.89 = 686.17/x
3. Step 3: Cross multiply
   1,209.79x = 1,669.89 × 686.17
4. Step 4: Simplify right side
   1,209.79x = 1,145,828.42
5. Step 5: Solve for x
   x = 1,145,828.42/1,209.79
6. Step 6: Final answer
   x = 947.13