Chem Help Please!!!?

Question

What is the half-life in minutes of a radioactive nuclide if 1 frasl; 128th of the original sample remains after 54.0 min ?

Answer 1

Okay, if in one-half life, you have reduced the concentration of a radionuclide by half, then how many half-lives does it take to get to 1/128?

1 half-life = ½ of the original
2 half lives = ½ * ½ = ¼ of the original
3 half lives = ½ * ½ * ½ = 1/8
4 half lives = 1/16
5 half lives = 1/32
6 half lives = 1/64
7 half lives = 1/128

So, 54 minutes = 7 half lives, thus:

t½ = 54/7 = 7.71 minutes