1. The force f applied to an object varies jointly as the mass m and the acceleration
a
2. The fare f of a passenger varies directly as the distance d of his destinations.
3. P varies directly as I and inversely as the square root of g.
4. The area A of a parallelogram varies jointly as the base band altitude h.
5. The length / of a person's shadow at a given time varies directly as the height h
of the person
6. The area A of a triangle is proportional to its height h.
7. At a constant voltage, the electric current I varies inversely as the resistance R
8. V varies jointly as I, w and h.
9. The volume V of a gas at constant temperature varies inversely as the pressure
p.
10. The altitude h of a triangle with constant area varies inversely as its base b.
11. The pressure p of a gas varies jointly as its density d and its absolute
temperature t.
12. The time t required to travel a given fixed distance is inversely proportional to
the rate r.
13. The force f of attraction between two bodies varies directly as the product of
their weights w and inversely as the square of the distance d between them.
14. The cost c of electricity varies directly as the kilowatt-hour consumption I.
15. A varies directly as the cube of b and inversely as the product of c and d.​