Answer:
25
Explanation:
Half life equation is:
A = A₀ (½)^(t / T)
where A is the final amount, A₀ is the initial amount, t is time, and T is the half life.
Given that A₀ = 100, t = 5, and T = 2.5:
A = 100 (½)^(5 / 2.5)
A = 100 (½)^2
A = 100 (¼)
A = 25
There will be 25 atoms left.
