Hydrogen-3 has a half-life of 12.35 years. what mass of hydrogen-3 will remain form a 100.0 mg initial sample after 5.0 years? a) 7 mg b) 24 mg c) 76 mg d) 18 mg

I haven't worked out the number, but it won't be necessary ... it's easy to pick the answer out of the choices that are given. ... The time (5 yrs) is less than the half-life (12.35 yrs), so more than half of the original sample (100mg) remains. Only one of the choices is more than 50 mg. (Can you find it ?)