Question

PLEASE HELP ME If a radioactive substance has an initial mass of 50 grams

and its mass halves every 5 years, what is the number of
grams remaining after 20 years?

Answer 1

Answer:
`3.125\ g`

Step-by-step explanation:

Given

Initial mass
`A_o=50\ g`

half-life is
`T_{(1)/(2)}=5\ years`

At any time the left amount is given by

`A=A_o2^{-\frac{t}{T_{(1)/(2)}}}\\\\\text{Insert the values}\\\\A=50\cdot 2^{-(20)/(5)}\\\\A=50\cdot 2^(-4)\\\\A=(50)/(16)\\\\A=3.125\ g`