Solution for Problem 4.2.1

The half-life of radioactive plutonium Pu226 is 24,360 years. 
How much of a 4,000 gram sample will remain after 30,000 years?

Solve

            Step

Find A using A = Ao2-t/h        Half-life formula
 Identify each part
 
Ao= 4000
initial amount
t = 30000
time in years
h = 24360
half-life in years
A = 4000(2)-30000÷24360  » 1703.5 Half-life formula

Interpret Þ There would be about 1703.5 grams of radioactive plutonium left after 30,000 years.

Calculator Help

Most calculators....use ^ or xy for exponent key
HINT: use these key strokes
4000× 2 ^ (-30000÷24360) [enter or =]
Half-life means there is half the original(initial) amount left after t years.