Radium decays according to the function where Q represents the quantity remaining after t years and k is the decay constant 0.00043. How long will take for 40g of radium to decay to 10g?

For this problem, we use the formula for radioactive decay which is expressed as follows:

An = Aoe^-kt

where An is the amount left after time t, Ao is the initial amount and k is a constant.

We calculate as follows:

An = 10 g

Ao = 40 g

k = 0.00043

An = Aoe^-kt

10 = 40e^-0.00043 (t)

t = 3223.94 years