Repeat the above, but use 10 dimes and 25 pennies. Let the dimes represent a radioactive isotope, such as carbon-14, while the pennies represent a nonradioactive isotope, such as carbon-12. Remove only the dimes when they land heads-up. Collect all the pennies, and add them to the dimes that landed heads-up. Questions: Does the number of pennies affect the behavior of the dimes? Say someone gives you two sets of coins. The first set contains 10 dimes and 25 pennies. The second set contains 2 dimes and 25 pennies. Which set of coins has gone through a greater number of tosses?
Which set provides the most “radioactivity” after a toss? Which set is analogous to a sample of once-living ancient material?

Data from Previous Problem

Throw ten coins onto a flat surface. Move aside all the coins that landed tails-up. Collect the remaining coins. After tossing them once again, remove all coins that landed tails-up. Repeat this process until all the coins have been removed. Can you see how this is related to radioactive half-life? In units of “tosses,” what is the average half-life of 25 coins? 50 coins? 1 million coins?