Two cars leave an intersection at the same time. One is headed south at a constant speed

Question:

Two cars leave an intersection at the same time. One is headed south at a constant speed of 30 miles per hour, and the other is headed west at a constant speed of 40 miles per hour (see the figure). Build a model that expresses the distance d between the cars as a function of the time t.

At t = 0, the cars leave the intersection.

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