100× 5 = 500m

I took four breaks.

100+4×10 =140 (seconds)

140 seconds to catch up with B.

Assuming that both A and B keep running, then the time for A to catch up with B is 100? (5-4)= 100 (seconds). If A and B run 100 meters and stop 10 seconds, it is equal to A run 100? 5=20 (second) rest 10 second, b run 100? 4=25 (second) rest 10 second. After running 100 second, should A stop 100 second? 20- 1=4 (times) * * with 100+ 10? 4= 140 (seconds), at this time, the distance that A has run is 500 meters; 130 seconds, B has already run 400 meters (at this time, he has rested three times for 30 seconds each time) and has been resting there until 140 seconds. Just as B was about to leave, A arrived and they really met. So it took 140 seconds for A to catch up with B.