The amount of a radioactive substance remaining after t years is given by the function f of t is equal to m times 0 point 5 raised to the t over h power , where m is the initial mass and h is the half-life in years. Iron has a half-life of 2 point 7 years. Which equation gives the mass of a 200 mathrm mg iron sample remaining after t years, and approximately how many milligrams remain after 12 years?
Answer
A
f of t is equal to 2 point 7 times 0 point 5 to the t th power ; 0 point 0 0 0 7 mathrm mg
B
f of t is equal to 2 point 7 times 0 point 5 raised to the t over 200 power ; 2 point 6 mathrm mg
C
f of t is equal to 200 times 0 point 5 to the t th power ; 0 point 0 5 mathrm mg
D
f of t is equal to 200 times 0 point 5 raised to the t over 2 point 7 power ; 9 point 2 mathrm mg