Multiple QUESTIONS PLEASE HELP!! How many half-lives would it take for half a sample of a radioactive isotope 1 point
to decay?

1 half-life
2 half-lives
3 half-lives
4 half-lives

Gold-198 is radioactive isotope, and it has a half-life of about 2.5 days. You have 100 grams of Golf-198. How many grams remain after 20 days?

3.125 grams
1.5625 grams
0.78125 grams
0.390625 grams

How many half-lives would it take for only 25% of the original radioactive isotope to remain

1 half-life
2 half-lives
3 half-lives
4 half-lives

A Sample of cobalt-69 As an activity of 3000 BQ. What will the activity be after 50 years Cobalt-60 has a half-life of 5 years.

23.4375
1.46484375
5.859375
2.9296875

How many days does it take 16.0g of Gold-198 to decay to 1.0g? (each half-life=2.69 days)

10 days
2.69 days
10.76 days
16 days