Finding the Third Proportional to 404.25 and 640.25

Step by Step Solution

1. Step 1: Write the proportion equation
   404.25 : 640.25 = 640.25 : x
2. Step 2: Convert to fraction form
   404.25/640.25 = 640.25/x
3. Step 3: Cross multiply
   404.25x = 640.25 × 640.25
4. Step 4: Simplify right side
   404.25x = 409,920.06
5. Step 5: Solve for x
   x = 409,920.06/404.25
6. Step 6: Final answer
   x = 1,014.03