Aditya covered a certain distance at some speed. Had he moved $3 \text{ km/h}$ faster, he would have taken $40 \text{ minutes}$ less. If he had moved $2 \text{ km/h}$ slower, he would have taken $40 \text{ minutes}$ more. The distance is: (in $\text{ km}$)

$A$ train goes from Ballygunge to Sealdah at an average speed of $20 \text{ km/h}$ and comes back at an average speed of $30 \text{ km/h}$. The average speed of the train for the whole journey is (in $\text{km/h}$)

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

$A$ boy started from his house by bicycle at $10:00\, a.m.$ at a speed of $12\, km/hr$. His elder brother started after $1\, hr\, 15\, mins$ by scooter along the same path and caught him at $1:30\, p.m.$ The speed of the scooter will be (in $km/hr$):

$A$ train travelling with a speed of $60 \, km/h$ catches another train travelling in the same direction and then leaves it $120 \, m$ behind in $18 \, seconds$. The speed of the second train is (in $km/h$):

Mohan walks from Tilak Nagar to Moti Nagar and back in a certain time at the rate of $3 \frac{1}{2} \, km/h$. But,if he had walked from Tilak Nagar to Moti Nagar at the rate of $3 \, km/h$ and back from Moti Nagar to Tilak Nagar at the rate of $4 \, km/h$,he would have taken $10 \, minutes$ longer. The distance between Tilak Nagar and Moti Nagar is (in $km$)