A radioactive substance of mass 768g has a half life of 3 years. After how many years does this substance leave only 6g undecayed?
-
A.
21 -
B.
18 -
C.
15 -
D.
12
Correct Answer: Option A
Explanation
(768 to 384 to 192 to 96 to 48 to 24 to 12 to 6)
7 x 3 = 21yrs