Question 3
An and Bình both travel from S to F along the perpendicular paths shown. An follows $S\to A_1\to A_2\to A_3\to A_4\to A_5\to A_6\to A_7\to A_8\to A_9\to F$. Bình follows $S\to B_1\to B_2\to F$. Their total distances are equal. Given $SA_1=30$ m and $SB_1=50$ m, find $A_2A_3+A_4A_5+A_6A_7$ in metres.
