if you started with 880 kilograms of radioactive pennies, how many would be non radioactive after 20 seconds of decay?

Question

anonymous · Answer

The half life of the radioactive pennies has to be given to find how much has turned into non-radioactive after an X amount of time

hang254 · Answer

so i have to find the half life of 880?

anonymous · Answer

Half life has to be given, it's not something you can find unless you have more information, such as "how much pennies are left after 20 seconds"

hang254 · Answer

well, on my chart, for 800 kilograms of radioactive pennies, after 20 secs, there only 49.5 left radioactive.

anonymous · Answer

so after 20 seconds, 49.5kg were left out of 800?

hang254 · Answer

yes

hang254 · Answer

after 25 secs: 27 kg left
after 30 secs: 14.5 kg left

anonymous · Answer

ok so lets just use the 20 seconds --> 49.5kg to calculate 1/2 life, the others would work too, but I just picked this one
|dw:1351823113777:dw|
where N(t) = amount of material left after t time
          N0 = amount of material initially
          t = time (seconds in this case)
          t1/2 = half-life (seconds in this case)
Plug numbers in and solve, tell me if you still need help.