This exercise uses the radioactive decay model. The half-life of strontium-90 i

Algebra
Tutor: None Selected Time limit: 1 Day

This exercise uses the radioactive decay model.

The half-life of strontium-90 is 28 years. How long will it take a 70-mg sample to decay to a mass of 53.2 mg? (Round your answer to the nearest whole number.)

 yr

Apr 15th, 2015

Let y=ae^(kt), a=70mg

Half life is 28 years, 35=70e^(28k), ln35=ln70+28k, k=(ln35-ln70)/28=-0.025

So 53.2=70e^(-0.025t), ln53.2=ln70-0.025t, t=(ln70-ln53.2)/0.025=11

Let me know how it goes, thanks.

Apr 15th, 2015

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