Questions in nuclei

Select	Question
	In a radioactive substance at $t = 0$, the number of atoms is $8 \times {10^4}$. Its half life period is 3 years. The number of atoms $1 \times {10^4}$ will remain after interval
	The half life period of radium is 1600 years. The fraction of a sample of radium that would remain after 6400 years is
	During a negative beta decay
	Some radioactive nucleus may emit
	Which can pass through 20 cm thickness of the steel
	The half-life period of radium is 1600 years. Its average life time will be
	What percentage of original radioactive atoms is left after five half lives
	Beta rays emitted by a radioactive material are
	Alpha rays emitted from a radioactive substance are
	In the given reaction $_z{X^A}{ \to _{z + 1}}{Y^A}{ \to _{z - 1}}{K^{A - 4}}{ \to _{z - 1}}{K^{A - 4}}$ Radioactive radiations are emitted in the sequence