Question

the loss of mass per year for an element as m(l) =238(1-.40)t what will the mass of the element be after 3 yearts

Answer 1

$m(t)=238\cdot(1-.40)^t$

To find what the mass will be after 3 years we replace t by 3 into the equation

$\begin{gathered} m(3)=238\cdot(0.6)^3 \\ m(3)=238\cdot(0.216) \\ m(238)=51.408 \end{gathered}$

the mass will be 51.408