Question 4
Vân travels from A to B and Phong from B to A.
• If they start at the same time, they meet after 3 hours.
• If Phong starts 90 minutes before Vân, they meet 2 hours 24 minutes after Vân starts.
How many minutes before Phong must Vân start so that, when they meet, Vân has travelled four times as far as Phong?
Model clarification: each travels at a constant speed, unchanged between the situations.
• If they start at the same time, they meet after 3 hours.
• If Phong starts 90 minutes before Vân, they meet 2 hours 24 minutes after Vân starts.
How many minutes before Phong must Vân start so that, when they meet, Vân has travelled four times as far as Phong?
Model clarification: each travels at a constant speed, unchanged between the situations.