Multiple choice

The distance between two cities $A$ and $B$ is $330\ km$. A train starts from $A$ at $8\ a.m.$ and travels towards $B$ at $60\ km/hr$. Another train starts from $B$ to $9\ a.m.$ and travels towards $A$ at $75\ km/hr$. At what time do they meet?

  1. $10\ a.m.$
  2. $10:30\ a.m.$
  3. $11\ a.m.$
  4. $11:30\ a.m.$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Train A travels for 1 hour alone (8am to 9am), covering 60 km. Remaining distance = 330 - 60 = 270 km. Relative speed = 60 + 75 = 135 km/hr. Time to meet = 270 / 135 = 2 hours after 9am, which is 11am.

AI explanation

By 9 a.m., the first train from A has traveled for one hour at 60 km/hr, covering a distance of 60 km, leaving a remaining distance of 330 minus 60 equaling 270 km. From 9 a.m. onwards, both trains travel towards each other, so we use the relative speed method by adding their speeds: 60 plus 75 equals 135 km/hr. The time taken to meet is the remaining distance divided by the relative speed, which is 270 divided by 135, equaling 2 hours. Adding these 2 hours to 9 a.m. gives the meeting time of 11 a.m.

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