What percentage of decay takes place in the average life of a substance ?

Deduce the relation between half life and average life of a radioactive substance.

Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.

7/8 of the original mass of a radioactive substance decays in 30 min. What is the half life of the radioactive substance ?

Assertion In one half-life of a radioactive substance more number of nuclei are decayed than in one average life. Reason Average life = Half -life/in (2)