Finding the Third Proportional to 405,686 and 636,380

Step by Step Solution

1. Step 1: Write the proportion equation
   405,686 : 636,380 = 636,380 : x
2. Step 2: Convert to fraction form
   405,686/636,380 = 636,380/x
3. Step 3: Cross multiply
   405,686x = 636,380 × 636,380
4. Step 4: Simplify right side
   405,686x = 404,979,504,400
5. Step 5: Solve for x
   x = 404,979,504,400/405,686
6. Step 6: Final answer
   x = 998,258.52