A car travels $60 \mathrm{km}$ with $3$ litres of petrol. If the car has to cover the distance of $200 \mathrm{km}$, it requires  litres of petrol.

Distance travelled by a bus and time taken are in direct proportion.

Expenditure of a family to number of members of the family are in direct proportion.

Number of students in a hostel and consumption of food are not in direct proportion.

If Mallika walks $1 \mathrm{km}$ in $20$ minutes, then she can cover $3 \mathrm{km}$ in $1$ hour.

If $12$ men can dig a pond in $8$ days, then $18$ men can dig it in $6$ days.