The radioactive substance cesium-137 has a half-life of 30 years. The amount A(t) in grams of cesium-137 remaining after t years is the following function

Question

A(t)=621(1/2)^t/30

 

Initial grams?

After 100 years?

Answer 1

To get the initial mass, set t = 0.

 

A(0) = 621 (1/2)^0/30 g = 621 (1) g = 621 g

 

To get the mass after 100 years, just plug t = 100 into A(t) and evaluate.

 

A(100) = 621 (1/2)^100/30 g = ? g