Finding the Third Proportional to 319.88 and 685.31

Step by Step Solution

1. Step 1: Write the proportion equation
   319.88 : 685.31 = 685.31 : x
2. Step 2: Convert to fraction form
   319.88/685.31 = 685.31/x
3. Step 3: Cross multiply
   319.88x = 685.31 × 685.31
4. Step 4: Simplify right side
   319.88x = 469,653.22
5. Step 5: Solve for x
   x = 469,653.22/319.88
6. Step 6: Final answer
   x = 1,468.24