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A tourist covers half of his journey by train at $60$ $km/h$, half of the remainder by bus at $30$ $km/h$ and the rest by cycle at $10$ $km/h$. The average speed of the tourist in $km/h$ during his entire journey is

1. $36$
2. $30$
3. $24$
4. $18$
edited | 1.4k views

Let the total distance be $D$ then

Avg speed $=\dfrac{D}{\text{total time taken}}$

Total time taken $=\left(\dfrac{D}{2} \times 60\right)+ \left(\dfrac{D}{4}\times 30\right)+ \left(\dfrac{D}{4}\times 10\right)$

$\text{Avg speed}- \dfrac{120}{5}=24.$
edited

Ans:24