If $A$ travels to his school from his house at the speed of $3 \, km/h$,he reaches the school $5 \, minutes$ late. If he travels at the speed of $4 \, km/h$,he reaches the school $5 \, minutes$ earlier than the scheduled time. The distance of his school from his house is (in $km$):

Two trains of equal length take $10\, seconds$ and $15\, seconds$ respectively to cross a telegraph post. If the length of each train is $120\, metres,$ in what time (in $seconds$) will they cross each other when travelling in opposite directions?

$A$ man starts from a place $P$ and reaches the place $Q$ in $7 \, hours$. He travels $\frac{1}{4}^{th}$ of the distance at $10 \, km/h$ and the remaining distance at $12 \, km/h$. The distance,in $km$,between $P$ and $Q$ is

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:

Two trains start at the same time from Delhi and Mumbai and move towards each other at the rate of $85 \, km/h$ and $65 \, km/h$ respectively. When they meet,it is found that one train has travelled $20 \, km$ more than the other. Find the distance between Delhi and Mumbai (in $km$).

$A$ car travels from $P$ to $Q$ at a constant speed. If its speed were increased by $10 \, km/h$,it would have taken $1 \, hour$ less to cover the distance. It would have taken a further $45 \, minutes$ less if the speed was increased by another $10 \, km/h$. The distance between the two cities is (in $km$):