A person travels frac{1}{3} of his journey by | vedclass

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(C) Let $S$ be the total distance of the journey.Time taken for the first $\frac{1}{3}$ of the journey at $60\, km/h$ is $t_1 = \frac{S/3}{60} = \frac

Vedclass · Accepted Answer

$20$

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(C) Let $S$ be the total distance of the journey.Time taken for the first $\frac{1}{3}$ of the journey at $60\, km/h$ is $t_1 = \frac{S/3}{60} = \frac{S}{180}$ hours.Time taken for the second $\frac{1}{3}$ of the journey at $30\, km/h$ is $t_2 = \frac{S/3}{30} = \frac{S}{90}$ hours.Time taken for the remaining $\frac{1}{3}$ of the journey at $10\, km/h$ is $t_3 = \frac{S/3}{10} = \frac{S}{30}$ hours.Total time taken $T = t_1 + t_2 + t_3 = \frac{S}{180} + \frac{S}{90} + \frac{S}{30}$.Taking the least common multiple $(LCM)$ of $180, 90, 30$,which is $180$:$T = \frac{S + 2S + 6S}{180} = \frac{9S}{180} = \frac{S}{20}$ hours.Average speed = $\frac{	ext{Total distance}}{	ext{Total time}} = \frac{S}{S/20} = 20\, km/h$.

$A$ person travels $\frac{1}{3}$ of his journey by bus at $60\, km/h$,$\frac{1}{3}$ by scooter at $30\, km/h$,and the rest by walking at $10\, km/h$. Find his average speed for the whole journey (in $km/h$).

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