You can
put this solution on YOUR website!Each half life, the amount (or fraction) remaining, becomes 1/2 of what it was before. So the fraction remaining after

years would be

So

= approximately 0.01=1/100 (or about 0.0106 if you want a couple more significant digits)
I would say that after 10,000 years about 1/100 (or 1%) of the substance is left.