$x$ fraction of a radioactive sample decay in $t$ time. How much fraction will decay in $2t$ time

Decay constant of radium is $\lambda $. By a suitable process its compound radium bromide is obtained. The decay constant of radium bromide will be

Draw a graph of the time $t$ versus the number of undecay nucleus in a radioactive sample and write its characteristics. 

The half life of radioactive Radon is $3.8\, days$. The time at the end of which $1/20^{th}$ of the Radon sample will remain undecayed is  ………… $days$ (Given $log_{10}e = 0.4343$ )

Write a formula showing the relation between half life and average life of a radioactive substance.