A sample of radium-226 contains 1.0×108 atoms of radium-226. How many atoms of radium-226 will remain in the sample after three half-lives?

Respuesta :

after 3 half lives it will be (1/2)^3 or 1/8 of original

so
1/8 times 10^8=1.25 x 10⁶ atoms left