21-kilometer 7555

A tourist moving at the same pace completes a 21-kilometer hike in 4 hours, taking a 30-minute break. Calculate the average speed of tourists.

Correct answer:

v =  6 km/h
v₂ =  5.25 km/h

Step-by-step explanation:

$$\begin{gathered} s=21\text{km} \\ {t}_1=4\text{h} \\ t=t_1-\frac{30}{60}=4-\frac{30}{60}=\frac{4\cdot 60}{60}-\frac{30}{60}=\frac{240}{60}-\frac{30}{60}=\frac{240-30}{60}=\frac{210}{60}=\frac{7}{2}=3.5\text{h} \\ v=s/t=21/\frac{7}{2}=21:\frac{7}{2}=21\cdot \frac{2}{7}=\frac{21\cdot 2}{7}=\frac{42}{7}=6\text{km/h} \end{gathered}$$

$v_2=s/t_1=21/4=5.25\text{km/h}$

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