Question

If element X has a half life of 25 years, what fraction of a sample of element X would remain after 50 years?

a.) 3/4
b.) 1/8
c.) 7/8
d.) 1/2
e.) 1/4

Answer 1

how many half-lives will pass after 50 years if each half-life is 25 years?

Answer 2

I don't know, 5?

Answer 3

what's 50 divided by 25?

Answer 4

2

Answer 5

so 25 years + 25 years = 50 years = 2 half-lives, ok so far?

Answer 6

yes.

Answer 7

so, after each half life, HALF of the sample will decay, no matter how much you started with, the amount will always be cut in half for the next half-life

Answer 8

so if you start with 100% of a sample, after one half life, you'll have 50% remaining.

Answer 9

after a SECOND half-life, half of the 50% will remain, and what's half of 50%?

Answer 10

25

Answer 11

so what's the fraction that means the same thing as 25%?

Answer 12

e?