Finding the Third Proportional to 405,628 and 636,280

Step by Step Solution

1. Step 1: Write the proportion equation
   405,628 : 636,280 = 636,280 : x
2. Step 2: Convert to fraction form
   405,628/636,280 = 636,280/x
3. Step 3: Cross multiply
   405,628x = 636,280 × 636,280
4. Step 4: Simplify right side
   405,628x = 404,852,238,400
5. Step 5: Solve for x
   x = 404,852,238,400/405,628
6. Step 6: Final answer
   x = 998,087.50