Iron-59 has a half-life of 44 days. a radioactive sample has an activity of 0.64 mbq. what is the activity of the sample after 88 days?

Radioactive decay is a pseudo-first order reaction. When you know the half-life of the material, you could use this equation.

A= A₀(1/2)^t/h
where 
A is the final activity
A₀ is the initial activity
t is the time
h is the half-life

A = (0.64)(1/2)^88/44 = 0.16 mbq

Density and pressure

Bis the answerhope it !