Hello,

I could use some help with the following question.

The half-life of is 5730 years. If a sample of has a mass of 20 micrograms at time 0, how long will it take until (a) 10 micrograms, and (b) 5 micrograms are left.

Here's what I have:

To solve, I use the exponential decay formula:

First, I solve for k:

But, here I am stuck, because the value of is a very long non-terminating decimal. How am I supposed to use this in the exponential decay formula?

thanks