VTMO 2026 - Grade 8 - Semifinal - SET 1 - Self-study Question 10

An, Bình and Châu travel from $A$ to $B$, starting at 6 a.m., 7 a.m. and 8 a.m., with speeds $20$, $30$ and $40$ km/h, respectively. At what time is Châu exactly halfway between An and Bình?