Find the missing slant height

Answer:
[tex]\ell=\frac{77}{4}[/tex]
Step-by-step explanation:
Because these two cones are similar, we can set up the following proportion:
[tex]\frac{11}{4}=\frac{\ell}{7}[/tex]
Solving, we get:
[tex]\ell=\frac{7\cdot11}{4},\\\ell=\fbox{$\frac{77}{4}$}[/tex].