Jaroslav 36791

Oldřich ran out of the house at 7.00 at 10 km/h. After 3 minutes, Jaroslav also ran at 12 km/h. A) what time did Jaroslav Oldřich finish? B) how many km did each run?

Result

t = 7:18 hh:mm
s =  73 km

Step-by-step explanation:

$$\begin{gathered} v_1=10\text{km/h} \\ {v}_2=12\text{km/h} \\ T=3\text{min}\to \text{h}=3:60\text{h}=0.05\text{h} \\ {s}_1=s_2 \\ {v}_1\cdot x=v_2\cdot (x-T) \\ 10\cdot x=12\cdot (x-0.05) \\ 2x=0.6 \\ x=\frac{0.6}{2}=0.3 \\ x=\frac{3}{10}=0.3 \\ t=7.00+x=7.00+0.3=7.3=7:18\text{hh}:\text{mm} \end{gathered}$$

$s=v_1\cdot t=10\cdot 7.3=73\text{km}$

Try another example