We want to know if the triangles shown, ABC and GHJ are similar.
We remember that two triangles are similar when their sides are proportional, and when its angles are congruent.
In this case, as we just have the sides, if we want to verify the similarity of the triangles, we are going to check if all sides are proportional. This is, if when we divide corresponding sides we obtain the same number.
Doing the divisions we get:
![\begin{gathered} (AC)/(JG)=\frac{12\operatorname{mm}}{6\operatorname{mm}}=2 \\ (CB)/(JH)=\frac{6\operatorname{mm}}{3\operatorname{mm}}=2 \\ (AB)/(GH)=\frac{16\operatorname{mm}}{8\operatorname{mm}}=2 \end{gathered}]()
As all the divisions are 2, this means that all sides are proportional, and then, the triangles are similar with coefficient of proportionality 2.
