A journey - 2 parts

A part of journey is covered in 1 h 40 min at 75 km/h and the remaining part of it is covered in 2 h 50 min at 60 km/h.Find the total length of the journey and average speed.

Correct answer:

s =  295 km
v =  65.56 km/h

Step-by-step explanation:

$$\begin{gathered} t_1=1:40=1hr40min=1+\frac{40}{60}=1.6667hr\doteq 1.6667 \\ {v}_1=75\text{km/h} \\ {t}_2=2:50=2hr50min=2+\frac{50}{60}=2.8333hr\doteq 2.8333 \\ {v}_2=60\text{km/h} \\ s=v_1\cdot t_1+v_2\cdot t_2=75\cdot 1.6667+60\cdot 2.8333=295\text{km} \end{gathered}$$

$$\begin{gathered} t=t_1+t_2=1.6667+2.8333=\frac{9}{2}=4.5\text{h} \\ v=\frac{s}{t}=\frac{295}{4.5}=65.56\text{km/h} \end{gathered}$$

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