A radio-active material is reduced to 1 / 8 of its original amount in 3 days. If 8 10⁻³ ~kg of the material is left after 5 days. The initial amount of the material is

Step-by-step solution

N = N ₀ ( 1 2 )^ n N = N ₀ 8 N ₀ 8 = N ₀ ( 1 2 )^ n ( 1 2 )^3= ( 1 2 )^ n n =3 3 half lives =3 days 1 half life =1 day 5 days =5 half life N = N ₀ ( 1 2 )^ n 8 10⁻³= N ₀ ( 1 2 )^5 N₀=2^5 8 10⁻³=256 gm