For the first order reaction, X→Y the time taken for 87.5% completion of the reaction is 180 minutes. Time taken for 99.9% completion of the reaction will be ------ minutes

t87.5%t50%=2.303K log 100100-87.52.303K log 100100-50; t87.5%t50%=3 log 2 log 2 t87.5%=3t50%; Conclusion :       t99.9%=10t50%;        t75%=2t50%;     t87.5%=3t50%;   t93.75%=4t50%; t 96.875%=5t50%;