word problem

[Guest]

Cobalt-60, which has a half life of 5.3 years, is extensively used in medical radiology. Most of the world's supply of cobalt-60 is produced in Canada.

a) What fraction of an orgional sample of cobalt-60 will remain after 10.6 years?

b) How long will it take until there is only 15.5% of the orgional sample remaining?

 

[Guest]

a) What fraction of an orgional sample of cobalt-60 will remain after 10.6 years?

It was halved each time 5.3 years passed. How many times is that?

b) How long will it take until there is only 15.5% of the orgional sample remaining?

How many times does 100% need to be halved to get 15.5%?

1 * (1/2)^x = 0.155