NCERT Class 8 Mathematics Chapter 13 Direct and Inverse Proportion CBSE Board Sample Problems

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Direct and Inverse Proportion

Direct and Inverse Proportion
Direct and Inverse Proportion

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Term

Description

1.

Direct Proportion

Two quantities x and y are said to be in direct proportion

If they increase (decrease) together in such a manner that the ratio of their corresponding values remains constant.

That is if {k is a positive number}= constant

Then x and y are said to vary directly. In such a case if are the values of y corresponding to the values x1, x2 of x respectively then

2.

Inverse proportion

Two quantities x and y are said to be in inverse proportion

If an increase in x causes a proportional decrease in y (and vice versa) in such a manner that the product of their corresponding values remains constant.

That is, if xy=k= constant

Then x and y are said to vary inversely.

In this case if y1, y2 are the values of y corresponding to the values x1 x2 of x respectively then

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