The radioisotope radon-222 has a half-life of 3.8 days. How much of a 73.9-gram sample of radon-222 would be left after approximately 23 days?

We use the formula of the half-life formula which is expressed as A = A₀ (1/2) ^ (t/h) where A is the final amount, A₀ is the initial amount of the substance, t is the time and h is the half-life of the substance which is equal to 3.8 days.

A = A₀ (1/2) ^ (t/h)

A = 73.9 (1/2) ^ (23 / 3.8)

A = 24.81.11 g of radon-222 left