The half life of bromine74 is 25 min how much of a 68mg samp

The half- life of bromine-74 is 25 min. how much of a 6.8mg sample is still active after 75 min?

Solution

Initially if we have 6.8 mg of bromine then after 25 min it will be = 6.8/2

                                                                                           = 3.4 mg

therefore after next 25 min or after total 50 min it will be = 3.4/2

                                                                                 = 1.7 mg

finally after next 25 min or after complete 75 min it will be = 1.7/2

                                                                                    = 0.85 mg