Mathematics

Problem

Car A is driving due north at a constant speed of

60\,\text{km/h}

and is currently

3\,

km north of an intersection. Car B is driving due east at

80\,\text{km/h}

and is currently

4\,

km east of the same intersection. At that instant, how fast is the straight-line distance between the two cars increasing? a)

140\,\text{km/h}

71.4\,\text{km/h}

100\,\text{km/h}

80\,\text{km/h}