Maths problem: how to do, thanks?

(a) least possible wt. of a regular pack of powder 
= 80-0.5 = 79.5 g

(b) 
least possible wt. of this pack of powder
= 79.5 g x 45 = 3577.5 g = 3.5775 kg = 3.6 kg (corr. to the nearest 0.1 kg) 

max. possible wt. of this pack of powder
= 80.5 g x 45 = 3622.5 g = 3.6225 kg = 3.6 kg (corr. to the nearest 0.1 kg) 

So, this pack of powder, 
which has a possible wt. in between 3.5775 & 3.6225 kg, 
can only be measured as 3.6 kg(corr. to the nearest 0.1 kg).
∴ it is not possible that the total wt. of this pack of powder to be measured as
3.5 kg, corr. to the nearest 0.1 kg