If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in 4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm
(a) In 8 minutes (b) In 12 minutes
(c) In 16 minutes (d) In 20 minutes
(b) 20 gm substance reduces to 10 gm (i.e. becomes half in 4 min. So = 4 min . Again
t = 12 min.