Finding the Third Proportional to 439.31 and 685.59

Step by Step Solution

1. Step 1: Write the proportion equation
   439.31 : 685.59 = 685.59 : x
2. Step 2: Convert to fraction form
   439.31/685.59 = 685.59/x
3. Step 3: Cross multiply
   439.31x = 685.59 × 685.59
4. Step 4: Simplify right side
   439.31x = 470,038.79
5. Step 5: Solve for x
   x = 470,038.79/439.31
6. Step 6: Final answer
   x = 1,069.94