MAT-1025 Midterm: MATH 1025 App State summer2012 Test2 answer key
Document Summary
Be sure to show your work: (14 points) the radioactive isotope appalachium-1025 decays at a rate of 2. 5% per day. We initially have 5 kilograms of this isotope. The decay rate is r = 0. 025 initial amount is a = The growth factor (i. e. base) is b = The amount of appalachium-1025 remaining after t days is f (t) = To nd how long until 1 kg is left we must solve f (t) = 1 which is 5 0. 975t = 1 so 0. 975t = 1/5 = 0. 2. Taking logs of both sides (i"ll use natural logs) we get ln(0. 975t) = ln(0. 2). Using a law of logs we have t ln(0. 975) = ln(0. 2). Alternatively, we could have graphed f (t) = 5 0. 975t along with the horizontal line y = 1 and found where they intersect. The half-life of appalachium-1025 is ln(2)/ ln(0. 975) 27. 3779.
