Question

here's ur question....​

Answer 1

$\color{darkblue}\underline{\underline{\sf Given-}}$

• A boy walks to jis school at distance = 6km
• With constant speed ${\sf (v_1)=2.6km/h}$
• And walk back with a constant speed of ${\sf (v_2)=4km/h}$

$\color{darkblue}\underline{\underline{\sf To \: Find-}}$

• Average speed for the round trip (in km/h)

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$\color{green}\underline{\underline{\sf Formula \: Used-}}$

$\color{violet}\blacksquare\underline{\boxed{\sf Average\: Speed(v_{av})=\dfrac{Total\: Distance (s)}{Total \: time(t)}}}$

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❏ Total Distance (s)

$\implies{\sf s=s_1+s_2}$

$\implies{\sf s = 6+6 }$

$\color{orange}\boxed{\sf s=12km }$

❏ Total Time (t)

$\implies{\sf t_1=\dfrac{s_1}{v_1} }$

$\implies{\sf t_1=\dfrac{6}{2.5}}$

$\color{orange}\implies{\sf t_1=\dfrac{12}{5}}$

$\implies{\sf t_2=\dfrac{s_2}{v_2} }$

$\implies{\sf t_2=\dfrac{6}{4} }$

$\color{orange}\implies{\sf t_2=\dfrac{3}{2} }$

$\implies{\sf t=t_1+t_2 }$

$\implies{\sf t=\dfrac{12}{5}+\dfrac{3}{2} }$

$\color{orange}\boxed{\sf t=\dfrac{39}{10} }$

$\Large\implies{\sf v_{av}=\dfrac{Total\: Distance}{Total\: time}}$

$\implies{\sf v_{av}=\dfrac{12}{\dfrac{39}{10}} }$

$\implies{\sf v_{av}=\dfrac{120}{39} }$

$\color{red}\implies{\sf v_{av}=\dfrac{40}{13}km/h}$

$\color{darkblue}\underline{\underline{\sf Answer-}}$

Option (b)

His Average speed for the round trip expression is $\color{red}{\sf \dfrac{40}{13}km/h}$.