Respuesta :

Rasco

Answer:

20.0 sec

you can use ln (2)=k* t1/2 then ln N2/N1=-k(t2-t1)

or just divide 100 by 2 then 50 by 2 then 25 by 2 then 12.5 by 2 and that is 4 half lifes at 5 secs each

Explanation: