Two cars leave the same parking lot, with one heading north and the other heading east. After several minutes, the northbound car has traveled 4 kilometers, and the eastbound car has traveled 4 kilometers. Measured in a straight line, how far apart are the two cars? If necessary, round to the nearest tenth.

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling