Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

The half life of radium is 1590 years. in how many years will one gram of pure element a) lose on centigram b) be reduced to one cetingram.

Half life equation i-e t-1/2 = 0.693/lamda

first i find lamda by the above formule but after that i use dn/dt=n * lamda . disintegration per sec. but didn't know how to put the values