$A$ motorist covered the first $20 \text{ km}$ of his journey in $30 \text{ minutes}$ and the remaining $29 \text{ km}$ in $40 \text{ minutes}$. His average speed in $\text{km/hr}$ is:

$A$ train passes two persons walking in the same direction at a speed of $3 \, km/h$ and $5 \, km/h$ respectively in $10 \, s$ and $11 \, s$ respectively. The speed of the train is (in $km/h$):

$P$ and $Q$ are $27 \, km$ apart. Two trains with speeds of $24 \, km/h$ and $18 \, km/h$ respectively start simultaneously from $P$ and $Q$ and travel in the same direction. They meet at a point $R$ beyond $Q$. The distance $QR$ is (in $km$):

Sound travels $330 \text{ m/s}$. If the sound of a thundercloud is heard $10 \text{ s}$ after the flash,the distance of the thundercloud is (in $\text{km}$):

Two men start together to walk a certain distance,one at $4 \, km/h$ and another at $3 \, km/h$. The former arrives half an hour before the latter. Find out the distance in $km$.

On a tour,a man travels at the rate of $64 \text{ km/h}$ for the first $160 \text{ km}$,then travels the next $160 \text{ km}$ at the rate of $80 \text{ km/h}$. The average speed in $\text{km/h}$ for the first $320 \text{ km}$ of the tour is: