Question

Bismuth-210 has a half-life of about 5 days.

After 15 days, how many milligrams of a 600 mg sample will remain?

Answer 1

It has "half-life of about 5 days"

You start with 600 mg. After 5 days, how much is left?

Answer 2

75?

Answer 3

what is half of 600?

Answer 4

300

Answer 5

so after 5 days you'll have 300 mg left

Answer 6

after another 5 days you'll cut that in half

so you'll be left with 300/2 = 150 mg

Answer 7

and finally, on day 15 (another set of 5 days later), you'll be left with 150/2 = 75 mg