Question

A block having 12g of an element is placed in a room. This element is a radioactive element with half-life of 15 yr. After how many years will there be just 1.5 g of the element in the box?

(a) 40 yr 

(b) 45 yr 

(c) 20 yr 

(d) 15 yr

Answer 1

Answer is (b) 45 yr