$A$ $75 \, m$ long train is moving at $20 \, km/h$. It will cross a man standing on the platform in (in $sec$):

$A$ person travels from $P$ to $Q$ at a speed of $40 \, km/hr$ and returns by increasing his speed by $50 \%$. What is his average speed for both the trips? (in $km/hr$)

$A$ train of $320 \, m$ crosses a platform in $24 \, s$ at a speed of $120 \, km/h$. $A$ man crosses the same platform in $4 \, min$. What is the speed of the man in $m/s$?

$A$ boy goes to his school from his house at a speed of $3 \, km/hr$ and returns at a speed of $2 \, km/hr$. If he takes $5 \, hours$ in total for the round trip,the distance between his house and school is (in $km$):

$A$ boy started from his house by bicycle at $10:00 \, am$ at a speed of $12 \, km/h$. His elder brother started after $1 \, hour \, 15 \, minutes$ by scooter along the same path and caught him at $1:30 \, pm$. The speed of the scooter was (in $km/h$):

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