For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is

Number of nuclei remainingN=600-450=150According to the law of radioactive decay,NN0=12tT1/2 ; where N0 is the number of nuclei initially. ∴  150600=12tT1/2; where T1/2= half life.  or 122=12tT1/2⇒t=2T1/2=2×10 minutes                                                            =20 minutes