Two boys are walking towards each other, and between them the dog is running, what path did the dog go during the time during

Two boys are walking towards each other, and between them the dog is running, what path did the dog go during the time during which the distance between the boys decreased from 300 to 100 m if the boys’ speeds are 3.5 and 3 km / h and the dogs are 10 km / h, the dog turns around instantly?

1). What is the distance covered by two boys walking towards each other, if the distance between the boys has decreased from 300 to 100 meters?
300 – 100 = 200 (meters);
200 m = 0.2 km.
2). What is the speed of convergence of boys, if it is known from the condition of the problem that the speed of boys is 3.5 and 3 km / h?
3.5 + 3 = 6.5 (km / h).
3). How long did the boys walk towards each other, and a dog ran between them?
0.2: 6.5 = 2/65 (hours).
4). What path did the dog run during the time during which the distance between the boys decreased from 300 to 100 meters, if the dog’s speed is 10 km / h and the dog turns around instantly?
10 2/65 = 4/13 ≈ 0.308 (km);
0.30769 km = 308 m.
Answer: 308 m.