Finding the Third Proportional to 639.56 and 727.31

Step by Step Solution

1. Step 1: Write the proportion equation
   639.56 : 727.31 = 727.31 : x
2. Step 2: Convert to fraction form
   639.56/727.31 = 727.31/x
3. Step 3: Cross multiply
   639.56x = 727.31 × 727.31
4. Step 4: Simplify right side
   639.56x = 528,983.47
5. Step 5: Solve for x
   x = 528,983.47/639.56
6. Step 6: Final answer
   x = 827.10