The amount of radium 226 remaining in a sample that originally contained A grams is approximately C(t) = A(0.999 567)t where t is time in years. Find the half-life to the nearest 100 years.

I assume you mean:

C_t = A(0.999567)^t

Do some calculation.

Let C be the initial amount of Radium.

C = A

When C halves, we get:

C' = A(0.999567)^t

Where:

C' = \frac{C}{2}

Replacing back, we get:

\frac{C}{2} = \frac{A}{2} = A(0.999567)^t

Therefore;

\frac12 = (0.999567)^t

Find the value of t.

Post what you get! :)