chemistry
posted by shaleena .
the mass of cobalt60 in a sample is found to have decreased from 0.800g to 0.200g in a period of 10.5 years. from this info calculate the halflife of cobalt60

ln(No/N) = kt
No = what you started with initially.
N = what you ended up with.
k = solve for this.
t = time in years.
Then plug k into the below equation.
k = 0.693/t_{1/2} and solve for t_{1/2}