# The half-life of cobalt-60 is 5.3 years. How many years will it take for 1/4 of the original amount of coblat-60 to remain?

##### 2 Answers

#### Answer:

It this not TWO half-lives.....?

#### Explanation:

After one-life,

And if a half-life is

How long until

#### Answer:

#### Explanation:

The half-life equation is :

What we know:

#t_("1/2")->"half-life"=5.3yrs.# #A_0->"Initial quantity"# #A(t)->"Amount left after t years"=1/4 A_0# #t->"time undergone"=color(blue)(?#

Substituting in the equation:

Take the

Dividend both sides by