For a substance the average life for `alpha-`emission is `1620` years and for `beta-`emission is `405` years. After how much time the `1//4` of the material remains after `alpha` and `beta` emission ?

For a substance, the average life for alpha -emission is 3240 years and for beta emission is 810 years. After how much time (in years) the one-fourth of the material remains by simultaneous emission? (ln 2=0.693) (Round of the answer to nearest integer.)

After 1 alpha and 2 beta emissions.

After 1 alpha and 2 beta emissions.

For a substance, the average life for alpha -emission is 1620 years and for beta emission is 405 years. If after (k xx 0.693) years, the one-fourth of the material remains by simultaneous emission, then find k

A radioactive material has mean lives of 1620 years and 660 years for alpha and beta emissions respectively the material decays by simultaneous alpha and beta emission. The time in which (1)/(4)th of the material remains intact is-