expoential and Logarithmic Models

Question

The half-life of Radium-226 is 1590 years. If a sample contains 100 mg, how many mg will remain after 1000 years?

Answer 1

Quantity remaining = initial quantity * (1/2)^[(time in years)/(1590 years)]

Quantity remaining = 100 mg * (1/2)^(1000/1590)

Quantity remaining ≈ 64.6655474644 mg

Quantity remaining ≈ 64.7 mg, rounded to a more realistic accuracy.