If the half-life of iodine-131 is 8 days, how old is a sample if only ¼ of the original amount remains? Write 2 - 3 sentences explaining your reasoning.

Question

nuts · Answer

Got any ideas how to approach the problem?

zarkam21 · Answer

8*1/4?

nuts · Answer

Let's think about half lives lol. if I have a sample of something with a half life of 5 days, 5 days later, how much of it remains?

zarkam21 · Answer

attachment

nuts · Answer

well it's called a half life not a life :P

zarkam21 · Answer

2.5

zarkam21 · Answer

because after 5 there will be half of its life left. which is 5/2=2.5

nuts · Answer

well I didn't tell you the original mass, but I think you're getting the idea.
Basically, if I had say 100 grams of a substance, and the half life was 5 days, after 5 days I'd only have 50 grams of that substance (and 50 grams of another substance)

zarkam21 · Answer

got it

nuts · Answer

I'll repost the original question for your convenience:

If the half-life of iodine-131 is 8 days, how old is a sample if only ¼ of the original amount remains? Write 2 - 3 sentences explaining your reasoning.

Got an idea how to approach it again?

zarkam21 · Answer

would it be 5?

zarkam21 · Answer

If the half-life of iodine-131 is 8 days, how old is a sample if only ¼ of the original amount remains, about 5 would be left of the sample

nuts · Answer

well the question is how old the sample is, right?

zarkam21 · Answer

yes

zarkam21 · Answer

Its 16 I GOT IT !

nuts · Answer

nice job :)
I'm headed off to bed, I guess some other benevolent soul might be able to help you at this hour ;)