RBSE Class 8 Maths Notes Chapter 13 Direct and Inverse Proportions

These comprehensive RBSE Class 8 Maths Notes Chapter 13 Direct and Inverse Proportions will give a brief overview of all the concepts.

RBSE Class 8 Maths Chapter 13 Notes Direct and Inverse Proportions

→ 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 \(\frac{x}{y}\) = k [k is s positive number], then x and y are said to vary directly. In such a case if y₁, y₂ are the values of y corresponding to the values x₁ x₂ of x recpectively then
\(\frac{x_{1}}{y_{1}}=\frac{x_{2}}{y_{2}}\) and \(\frac{x_{1}}{y_{1}}=\frac{x_{2}}{y_{2}}=\frac{x_{3}}{y_{3}}\) = .............. k

→ 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, then x and y are said to vary inversely. In this case y₁, y₂ are the values of y corresponding to the values x₁ x₂ of x respectively then x₁y₁ = x₂y₂ or \(\frac{x_{1}}{x_{2}}=\frac{y_{2}}{y_{1}}\) and x₁y₁ = x₂y₂ = x₃y₃ = k.