Question 9
An and Binh take equal-length routes from $S$ to $F$. An: $S$→A $_{1}$→A $_{2}$→A $_{3}$→A $_{4}$→A $_{5}$→A $_{6}$→A $_{7}$→A $_{8}$→A $_{9}$→$F$; Binh: $S$→$B _{1}$→$B _{2}$→$F$. $SB _{1} = 50 m$ and $SA _{1} = 30 m$; see the diagram. Find A $_{2}$ A $_{3}$+A $_{4}$ A $_{5}$+A $_{6}$ A $_{7}$ in metres.
