If you start with 80 grams of cobalt-60, how many grams will remain after three half-lives?

Use the formula for the remaining amount after n half-lives: \(\text{Remaining amount} = \text{Initial amount} \times \left(\frac{1}{2}\right)^n\).

Substitute the given values into the formula: \(\text{Remaining amount} = 80 \times \left(\frac{1}{2}\right)^3\).