A radioactive material has half-life of 10 days. What fraction of the material would remain after 30 days?

If N be the number of atoms of a radioactive substance left at some instant of time, thanN=N012nwhere N0 is the initial number of atoms and n is number of half lives.∴n=tT/2=3010=3∴NN0=123=123=18=0.125