Fast ? ? an isotope of chlorine has a half life of 55.5 minutes. if we start with 45 kilograms of this isotope, how much will remain after 3.7 hours?

 The  amount   that will remain after 3.7  hours  for isotope  chlorine that has a half  life   of 55.5  minutes  is 2.813  kg

 Explanation

Half  life  is the  time required for the  radio activity  of  a specified isotope  to  fall  to  a  half its  original value.

convert 3.7  hrs  into  minutes

= 3.7  x 60 = 222 minute

 find the number of half life  that chlorine  isotope undergo   in  222  minutes

=222  minutes /  55.5   minutes = 4  half life

therefore   45 kg after first half life  =45 kg /2=22 .5 kg

                  22.5  kg after second  half life =  22.5/2 =11.25  kg

                 11.25  kg after third half life  = 11.25/2 = 5.625 kg

                5.625  kg  after  fourth  half life =  5.625/2 = 2.813 kg

the actual answer was 160934