If on September 1 a school purchased a radioisotope of mass 350 g with a half-life of 45 days how much of the sample would be left on June 1?

Answer 1

Find the number of days (I refuse to futz around with a calendar for you). Divide it by the half-life, in this case 45 days. Raise 0.5 to that power (that's what the xy key on calculators is for). Multiply the resulting number by the original mass (here, 350 g) and there's your answer.

Answer 2

Assuming the radioisotope decays continuously, you can use the exponential decay formula: N(t) = N₀ * (1/2)^(t/T), where N(t) is the amount remaining at time t, N₀ is the initial amount, T is the half-life, and t is the time elapsed. Plugging in the values, the amount left on June 1 (t = 106 days) would be approximately 23.5 grams.