Which of the following are in inverse proportion?

Two quantities are in inverse proportion only if one of them increases and the other decreases.
i) Inverse proportion ⇒ If number of workers increases, then the time to complete job decreases.
ii) Not Inverse proportion ⇒ If time taken for a journey increases, then the distance travelled at uniform speed remains same.
iii) Not Inverse proportion ⇒ If area of cultivated land increases, then harvested crop will also increase.
iv) Inverse proportion ⇒ If time taken for a fixed journey increases, then the speed of vehicle decreases, so it is in inverse proportion.
v) Inverse proportion ⇒ If population of a country increases, then the area of land per person decreases.
∴ (i), (iv) and (v) are in inverse proportion.