Hi
einstein801, I am no expert but I believe this will answer your query.
If you find the relative speed while they travel in the same direction, it will be 10-5=5m/s.
We know the circumference is 400m, and time = distance/speed; thus, the time it takes for them to meet every time is 400/5=80 secs.
Given that they travel for a total of 40 mins i.e. 40*60=2400 secs.
So, the total number of times they will meet is 2400/80=30. This is the answer.
Or, you can do it this way too.
The relative speed in the same direction is 10-5=5m/s.
We know, distance=speed*time; so in 40 mins they cover 40*60*5=12000 m distance.
Given that the circumference is 400m, so the number of laps they cover i.e. the number of times they meet is 12000/400=30.
I hope this helps.
einstein801
Hi
MartyMurray Bunuel any idea how to tackle this question if they travel in the SAME direction?