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 = initial 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)^{20}=1.0775794222\approx1.1\text{ gram}[/tex]
Hence, the mass of the remaining element = 1.1 grams .
