Question

Tom was playing fetch in the park with his Jack Russell terrier. On one throw, the ball landed 90 meters from the terrier, and the terrier started running toward it at 11 meters per second. At the same time, a greyhound that was 140 meters away from the ball started running toward it at a speed of 19 meters per second.
If each dog kept a constant speed, how long did it take for both dogs to be the same distance from the ball?

Answer 1

Let t be seconds after they start. Their distances from the ball are 90 - 11t and 140 - 19t. Set equal:
90 - 11t = 140 - 19t
8t = 50
t = 50/8 = 25/4 = 6.25 seconds.