Finding the Fourth Proportional to 1,238.78, 1,709.24 and 714.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,238.78 : 1,709.24 = 714.72 : x
2. Step 2: Convert to fraction form
   1,238.78/1,709.24 = 714.72/x
3. Step 3: Cross multiply
   1,238.78x = 1,709.24 × 714.72
4. Step 4: Simplify right side
   1,238.78x = 1,221,628.01
5. Step 5: Solve for x
   x = 1,221,628.01/1,238.78
6. Step 6: Final answer
   x = 986.15