Question: The half-life of strontium-90, 90Sr, is 25 years. This means that half of any given quantity of 90Sr will disintegrate in 25 years.
(a) If a sample of 90Sr has a mass of 24 mg, find an expression for the mass that remains after t years.
(b) Find the mass remaining after 40 years, correct to the nearest milligram.
(c) Use a graphing device to graph m(t) and use the graph to estimate the time required for the mass to be reduced to 5 mg.