$A$ car travels the first one-third of a certain distance with a speed of $10\, km/hr$,the next one-third distance with a speed of $20\, km/hr$,and the last one-third distance with a speed of $60\, km/hr$. The average speed of the car for the whole journey is (in $km/hr$):

$A$ dog finds a cat at $25$ leaps away. The cat sees the dog coming towards it and starts running with the dog in hot pursuit. In every minute, the dog makes $5$ leaps and the cat makes $6$ leaps, and one leap of the dog is equal to $2$ leaps of the cat. Find the time in which the dog will catch the cat (in minutes).

$A$ person covers a certain distance in $6 \, hours$ if he travels at $40 \, km/h$. If he has to cover the same distance in $4 \, hours$,then his speed must be (in $km/h$):

$A$ train $180 \, m$ long is running at a speed of $90 \, km/h$. How long will it take to pass a post? (in $sec$)

$A$ man goes from a place $A$ to $B$ at a speed of $12 \, km/h$ and returns from $B$ to $A$ at a speed of $18 \, km/h$. The average speed for the whole journey is? (in $km/h$)

$A$ train completes a non-stop journey in $8 \, \text{hours}$. If it had travelled $5 \, \text{km/h}$ faster, it would have completed the journey in $6 \, \text{hours} \, 40 \, \text{minutes}$. What is its lowest speed in $\text{km/h}$?