1. Dima is driving on a straight highway from point A to point B. From point B, a traffic jam is moving towards Dima, and the length of the jam is increasing at a speed of $v$ km/h. The speed of the car in the traffic jam is 10 km/h, and outside the jam - 60 km/h. The navigator in the car shows at any moment how much time is left for Dima to reach point B, based on the length of the traffic jam at that moment. At some point (before reaching the traffic jam), Dima noticed that the navigator shows the same time as it did a few minutes ago. Find $v$.