Finding the Fourth Proportional to 1,238.89, 1,709.67 and 686.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,238.89 : 1,709.67 = 686.89 : x
2. Step 2: Convert to fraction form
   1,238.89/1,709.67 = 686.89/x
3. Step 3: Cross multiply
   1,238.89x = 1,709.67 × 686.89
4. Step 4: Simplify right side
   1,238.89x = 1,174,355.23
5. Step 5: Solve for x
   x = 1,174,355.23/1,238.89
6. Step 6: Final answer
   x = 947.91