What is the half-live of a radioactive isotope if it takes 6.2 days for a 72g sample to decay to 18g?

i believe it is 40–40–20%

explanation:

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

i think its 100.

hope this !