How long will a boy take to run round a square field of side $35 \mathrm{metres}$, if he runs at the rate of $9 \mathrm{km}/\mathrm{hr}$?

A boy goes to his school from his house at a speed of $3 \mathrm{km}/\mathrm{hr}$ and returns at a speed of $2 \mathrm{km}/\mathrm{hr}$. If he takes $5 \mathrm{hours}$ in going and coming, find the distance between his house and school.

An aeroplane travels distances of $2500 \mathrm{km}$, $1200 \mathrm{km}$, and $500 \mathrm{km}$ at the rate of $500 \mathrm{km}/\mathrm{hr}$, $400 \mathrm{km}/\mathrm{hr}$, and $250 \mathrm{km}/\mathrm{hr}$respectively. Find the average speed of the plane.

A scooterist goes to a place at a speed of $20 \mathrm{km}/\mathrm{hr}$ and returns from there at a speed of $30 \mathrm{km}/\mathrm{hr}$. Find the average speed in $\mathrm{km}/\mathrm{hr}$ for the entire journey.

A train $280 \mathrm{m}$ long is moving at a speed of $60 \mathrm{km}/\mathrm{hr}$. What is the time taken by it to cross a platform $220 \mathrm{m}$ long?

A train is running at a speed of $90 \mathrm{km}/\mathrm{hr}$. If it crosses a signal in $10 \mathrm{seconds}$, find the length of the train in $\mathrm{metres}$.

A train $150 \mathrm{m}$ long passes a tree in $12 \mathrm{seconds}$. How long will it take to pass a tunnel $250 \mathrm{m}$ long?

A train speeds past a pole in $15 \mathrm{seconds}$ and a platform $100 \mathrm{m}$ long in $25 \mathrm{seconds}$. Find the length of the train.