MathNet 2016-part-07 — 182 problems (EN–VI) Question 148

Two circles centered at $O_{1}$ and $O_{2}$ have radii $2$ and $3$ and are externally tangent at $P$. The common external tangent of the two circles intersects the line $O_{1} O_{2}$ at $Q$. What is the length of $PQ$?