Intersection 81457

Two cars started from the right-angled intersection of two roads. The first at a speed of 80 km/h and the second at a speed of 60 km/h. How fast are they moving away from each other?

Correct answer:

v =  100 km/h

Step-by-step explanation:

$$\begin{gathered} v_1=80\text{km/h} \\ {v}_2=60\text{km/h} \\ s=s_1^2+s_2^2 \\ (v\cdot t{)}^2=(v_1\cdot t{)}^2+(v_2\cdot t{)}^2 \\ {v}^2=v_1^2+v_2^2 \\ v=\sqrt{v_1^2+v_2^2}=\sqrt{80^2+60^2}=100\text{km/h} \end{gathered}$$

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