You know that 4 out of 10 adults buy their drugs at large drug stores. To calculate the value of the proportion you have to divide 4 by 10
[tex]\begin{gathered} p=\frac{4}{10} \\ p=0.4 \end{gathered}[/tex]The city has n=34,000 adults, to determine the expected number of adults that buy at large drugstores, you have to multiply the total number of adults by the proportion:
[tex]E(X)=np[/tex]n=34,000 and p=0.4
[tex]\begin{gathered} E(X)=34000\cdot0.4 \\ E(X)=13600 \end{gathered}[/tex]Out of the 34,000 you could expect 13,600 adults to buy at large drug stores.
