Question

A sample of radioactive material starts with 80 grams. After 3 half-lives have passed, how much radioactive sample remains?

Answer 1

I want to say 10 grams

Step-by-step explanation:

80 grams is your start

and a half-life is half of that so...

half of 80 ( and or 80/2)

40 grams

then another half is...

half of 40 (and or 40/2)

20 grams

then another half-life is...

half of 20 (and or 20/2)

10 grams

That is 3 half-life of 80 grams

*becareful not to just divide 80 / 3 you will get 26.666 (repeating) that is incorrect

you want a half of a half of a half