A radioactive substance is decaying according to the equatio

A radioactive substance is decaying according to the equation Q (t) = Q, e^-0.00133 t years. After how many years the remaining quantity of this substance will 70% of the quantity in the beginning. Round your answer to nearest year.

Solution

Q (t) = Qo*e^(-0.00133*t)

0.7 = e^(-0.00133*t)

ln 0.7 = -0.00133*t

t =268.18 years