Finding the Third Proportional to 405.28 and 629.72

Step by Step Solution

1. Step 1: Write the proportion equation
   405.28 : 629.72 = 629.72 : x
2. Step 2: Convert to fraction form
   405.28/629.72 = 629.72/x
3. Step 3: Cross multiply
   405.28x = 629.72 × 629.72
4. Step 4: Simplify right side
   405.28x = 396,545.70
5. Step 5: Solve for x
   x = 396,545.70/405.28
6. Step 6: Final answer
   x = 978.45