Question

The following table shows the currently accepted half-life values for six parent isotopes.

Answer 1

@mrdoldum Is it potassium-40?

Answer 2

@gamer456148 There are two. There is one other that has a half-life short enough.

Answer 3

I mean c

Answer 4

@mrdoldum

Answer 5

one of the uraniums has a half life of only 700 some million years.

Answer 6

Yeah but out of the 4 choices the answer is the potassium-40 right? @mrdoldum

Answer 7

and the uranium. it seems to ask for all not just one.

Answer 8

Choices:

Potassium-40

Rubidium-87

Samarium-147

Uranium-238

Answer 9

My original guess was A

Answer 10

It would be Potassium-40 due to its half-life value being less than the Earth's age

Answer 11

You are right, A is correct @gamer456148

Answer 12

It asks for which would have less than 50% and the uranium with a 700 million year halflife would also be less than 50%

Answer 13

@mrdoldum I got it wrong it was Uranium-235

Answer 14

@gamer456148 @alphadxg I crap guys, it is too late for me. I just noticed the uranium I am talking about is not in the choices. Wait, you go it wrong? What did you put?

Answer 15

I was looking at the wrong one also

Answer 16

Potassium - 40 should be one of the right answers.

Answer 17

K-40 would be less than 50% though and none of the others in the list could possibly be less than 50% @alphadxg @gamer456148

Answer 18

:)

Answer 19

@alphadxg @gamer456148 K-40 could go through at least three half-lives in that time. Probably the person that wrote it meant to ask which one would be very close to 50% of original.

Answer 20

I don't know I got to go and start more homework. Final exams are in couple days and I have 7 study guides to complete.

Answer 21

Here think of it like this,

Answer 22

Half life = Time (Earth's life team) -> Percentage = 50%
Half life < Time (Earth's life team) -> Percentage < 50%
Half life > Time (Earth's life team) -> Percentage > 50%

Answer 23

Hope that helps

Answer 24

okay

Answer 25

@alphadxg @gamer456148 Still, quite annoying. That question just asks for less than 50%, that is all and K-40 and uranium 235 both would be less then 50%.

Answer 26

I'd complain to the teacher about it.

Answer 27

Yeah because I didn't know which too choose.

Answer 28

@gamer456148 Can't stand it when these things happen to students. How does it help you? It doesn't it makes studying harder.

Answer 29

:P