Grandmother

Mom walked out to visit her grandmother in a neighboring village 5 km away and moved at a speed of 4 km/h. An hour later, father drove down the same road at an average speed of 64 km/h.

1) How long will it take to catch Mom?
2) What is the approximate distance in meter meters? (round to an integer)

Final Answer:

t =  4 min
s =  4267 m

Step-by-step explanation:

$$\begin{gathered} v_1=4\text{km/h} \\ {v}_2=64\text{km/h} \\ {v}_1\cdot (1+T)=v_2\cdot T \\ 4\cdot (1+T)=64\cdot T \\ 60T=4 \\ T=\frac{4}{60}=0.06666667 \\ T=\frac{1}{15}\doteq 0.066667 \\ t=T\to \text{min}=T\cdot 60\text{min}=0.0667\cdot 60\text{min}=4\text{min}=4\text{min} \end{gathered}$$

$$\begin{gathered} s_1=64\cdot T=64\cdot 0.0667=\frac{64}{15}\doteq 4.2667\text{km} \\ s=s_1\to \text{m}=s_1\cdot 1000\text{m}=4.2667\cdot 1000\text{m}=4267\text{m}=4267\text{m} \end{gathered}$$

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