Finding the Fourth Proportional to 1,238.72, 1,709.48 and 686.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,238.72 : 1,709.48 = 686.72 : x
2. Step 2: Convert to fraction form
   1,238.72/1,709.48 = 686.72/x
3. Step 3: Cross multiply
   1,238.72x = 1,709.48 × 686.72
4. Step 4: Simplify right side
   1,238.72x = 1,173,934.11
5. Step 5: Solve for x
   x = 1,173,934.11/1,238.72
6. Step 6: Final answer
   x = 947.70