Question

A radioactive substance decays exponentially. A scientist begins with 190 milligrams of a radioactive

substance. After 33 hours, 95 mg of the substance remains.
How many milligrams will remain after 51 hours?
mg
Give your answer accurate to at least one decimal place.
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Answer 1

Answer: 65.1 (mg)

Explanation:

`y=190*e^(-a*t)\\\\Calculate\ a:\\\\t=33,y=95(mg)\\\\190*e^(-a*33)=95\\\\e^(-a*33)=0.5\\\\-a*33=ln(0.5)\\\\a=(ln((1)/(2)) )/(-33) \\\\a=0,02100... \approx{0.021}\\\\If\ t=51\ h, y=190*e^(-0.02100*51)=65.09167...\approx{65.1}`