posted by Anonymous .
A particular radioactive substance has a half-life of 4 minutes. How long will it take for 250 g of this radioactive material to decay to less than 0.1g?
I got 32 min but that not one of the choices. Please help
How many half lives does it go through to get from 250 g to < 0.1g?
# half lives x 4 min = ?