\(n_{HCl\left(1M\right)}=0,1.1=0,1\left(mol\right)\)
\(n_{HCl\left(1,5M\right)}=\left(0,1+0,4\right).1,5=0,75\left(mol\right)\)
\(\Rightarrow n_{HCl\left(aM\right)}=0,75-0,1=0,65\left(mol\right)\)
\(\Rightarrow C_{M_{ddHCl\left(aM\right)}}=\dfrac{0,65}{0,4}=1,625M\)
⇒ a = 1,625