Answer:
16 gram
explanation:
times it ionises/decays = [tex]\frac{4}{2}[/tex] = 2 times
we will divide by 2, two times, because it decays two times.
Left after 4 hours: 64 ÷ 2 ÷ 2 = 16 gram
OR
By using the formula: [tex]\frac{m}{2^{n} }[/tex] .....where m is the mass and n is times it decays.
times it decays: 4 ÷ 2 = 2 times
Left after ionising: [tex]\frac{64}{2^2}[/tex] = 16 gram.
