math
posted by Eric .
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

In en.wikipedia type: "Halflife"
and read text, and retype formulas.
So:
N(t)=N0*e^(lambda*t)
N(t)=N(17)=3
N0=10
t=17
3=10*e^(lambda*17) Divide with 10
3/10=e^(lambda*17)
e^(lambda*17)=3/10
lambda*17=ln(3/10)Divide with 17
lamba=ln(0.3)/17
lamda=ln(0.3)/17
lamda=(1,203972804326)/17
lamda=1,203972804326/17
lamda=0,07082193