Answer: The mass of the remaining element = 1.1 grams .
Step-by-step explanation:
Exponential equation of decay: [tex]y=A(1-r)^x[/tex] ...(i), where A = intial value , r= rate of decay in decimal , x= time.
As per given :
Initial mass : A= 140 grams
Rate of decay : r= 21.6% per minute= 0.216 per minute.
x= 20 minutes
Substitute values in (i) , we get
[tex]y=140(1-0.216)^20\\\\=140(0.784)^2^0=1.077579422[/tex]
Hence, the mass of the remaining element = 1.1 grams .
