Ex.13.2 Q1 Direct and Inverse Proportions Solution - NCERT Maths Class 8

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Question

 Which of the following are in inverse proportion?

(i) The number of workers on a job and the time to complete the job.

(ii) The time taken for a journey and the distance travelled in a uniform speed.

(iii) Area of cultivated land and the crop harvested.

(iv) The time taken for a afixed journey and the speed of the vehicle.

(v) The population of a country and the area of land per person.

Text Solution

Reasoning:

If two quantities are related in such a way that an increase in one quantity leads to a corresponding proportional decrease in the other, then such a variation is called inverse proportion.

Steps:

(i) The number of workers on a job and the time to complete the job.

Ans:  As the number of workers increase; the job will take less time to complete. Hence, they are inversely proportional.

(ii) The time taken to a journey and the distance travelled in a uniform speed.

Ans:  For more time, more distance to travel. Hence, they are not inversely proportional.

(iii) Area of cultivated land and the crop harvested.

Ans:  More area of land cultivated, more crop to harvest .Hence, they are not inversely proportional.

(iv) The time taken for a afixed journey and the speed of the vehicle.

Ans: If speed is increased, it will take less time to complete the fixed journey. Hence, they are inversely proportional.

(v) The population of a country and the area of land per person.

Ans: If the population of a country increases, then the area of land per person will be decreased. Hence, they are inversely proportional.