Question

Cobalt-60 has half-life of about 5 years. After 20 years, how many grams of a 2,076 gram sample will remain? Round to the hundredth place if answer doesn’t have a tenths use a zero so the answer does.

Answer 1

Givn the following question:

Half-life is equal to 5 years

Every 5 years its life gets halved.

Find the amount after 20 years

`\begin{gathered} 2076/(1)/(2)=1038=5\text{ years} \\ 1038/(1)/(2)=519=10 \\ 519/(1)/(2)=259.5=15 \\ 259.5/(1)/(2)=129.75=20 \\ 129.75=20\text{ years} \end{gathered}`

129.75 is your answer.