Question

Iodine-131, a radioactive substance that is effective in locating brain​ tumors, has a​ half-life of only eight days. a hospital purchased 22 grams of the substance but had to wait seven days before it could be used. how much of the substance was left after seven ​days?

Answer 1

5 days/8 days = 0.625 half lives 

fraction left after 0.625 half lives = (1/2)^0.625 

= 0.6484197773 

Amount left = 20*0.6484197773 gms 

= 12.97 gms to dp <<<