Which of the following quantities vary inversely as each other?
(i) The number of x men hired to construct a wall and the time y taken to finish the job.
(ii) The length x of a journey by bus and price y of the ticket.
(iii) Journey (x km) undertaken by a car and the petrol (y litres) consumed by it.
(i) Varies inversely.
Since the time taken to construct the wall varies with the number of men hired. If the number of men hired is increased then time required for constructing wall shall decrease and vice-versa.
(ii) Varies directly.
Since the cost of bus journey will vary with distance. If the distance of journey will increase then cost of ticket will increase and vice-versa.
(iii) Varies directly.
Since the quantity of petrol required varies with the distance. If the distance of journey will increase then petrol required will also increase and vice-versa.