Question

A person covers 60 km of the journey with a speed of 30 km/h

and again 120 km with a speed of 60 km/h. Find the average speeed

of the journey.​

Answer 1

$\Huge{\textbf{\textsf{{\green{Ans}}{\red{wer}}{\color{pink}{:}}}}}$

$average \: speeed \: \overline{V}\:= \frac{total \: distance}{total \:ti me} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{s_1 + s_2}{t_1 + t_2} \: \: - - - (1)\\ We\:know \:that\:,\\S\:=vt \\ Now\:first \: case \: : - \\ t_1 = \frac{s_1}{v_1} = \frac{60}{30} = 2 \: hours \\ \\ second \: case \: :- \\ t_2 = \frac{s_2}{v_2} = \frac{120}{60} = 2 \: hours \\ now \: from \: eqn.(1) \: \implies \\ average \: speeed \: = \frac{60 + 120}{2 + 2} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \overline{V}\: = \frac{200}{4} = 50 \: km {h}^{ - 1}$