Analysis: ∵ A is 75 meters away from B and B is 30 meters away from C, but the title does not explain the mutual position of the three people at the starting point, so it is necessary to discuss the mutual position of the three people. From the mutual position of Serie A, B and C, there are two possibilities:
(1) A is at the end, B is in the middle and C is in the front;
(2) A is at the end, C is in the middle and B is in the front;
(1) Analysis: ∵ The length of circular track is 150, the distance between A and B is 75m, and the distance between B and C is 30m. A, B and C run at the speed of V 1=7m, V2=2m and V3=4m per second respectively.
Let the meeting time be T. At the beginning, A comes last, B is in the middle and C is in the front.
The distance between Party A and Party B is 75, and that between Party A and Party C is 105.
7t/ 150 (take the remainder) =(2t+75)/ 150 (take the remainder) =(4t+ 105)/ 150 (take the remainder).
When t= 135, the above formula holds.
(2) Analysis: When starting, A is at the end, C is in the middle, and B is in front.
The distance between a and b is 75, and the distance between a and c is 45.
7t/ 150 (take the remainder) =(4t+45)/ 150 (take the remainder) =(2t+75)/ 150 (take the remainder).
When t= 15, the above formula holds.