# Direct and Inverse Proportions class 8 Notes Mathematics

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## Class 8 Mathematics notes Chapter 13 Direct and Inverse Proportions

Download CBSE class 8th revision notes for chapter 13 Direct and Inverse Proportions in PDF format for free. Download revision notes for Direct and Inverse Proportions class 8 Notes and score high in exams. These are the Direct and Inverse Proportions class 8 Notes prepared by team of expert teachers. The revision notes help you revise the whole chapter 13 in minutes. Revision notes in exam days is one of the best tips recommended by teachers during exam days.

## CBSE Class 8 Revision Notes Maths Direct and Inverse Proportions

• Variations: If the values of two quantities depend on each other in such a way that a change in one causes corresponding change in the other, then the two quantities are said to be in variation.
• Direct Variation or 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 ${x} \over {y}$=k [k is a 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, x  of x respectively then ${x_1} \over {y_1}$ = ${x_2} \over {y_2}$.
• If the number of articles purchased increases, the total cost also increases.
• More than money deposited in a bank more is the interest earned.
• Quantities increasing or decreasing together need not always be in direct proportion, same in the case of inverse proportion.
• When two quantities x and y are in direct proportion (or very directly), they are written as.$x \propto y$ Symbol $\propto$stands for ‘is proportion to’.
• 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, 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, xof x respectively then  x1, Y1 = x2, y2 or ${x_1} \over {y_1}$ = ${x_2} \over {y_2}$
• When two quantities x and y are in inverse proportion (or vary inversely), they are written as x $x \propto {{1} \over {y}}$. Example: If the number of workers increases, time taken to finish the job decreases. Or If the speed will increase the time required to cover a given distance will decrease.

## Direct and Inverse Proportions class 8 Notes Mathematics

Direct and Inverse Proportions class 8 Notes Mathematics. CBSE quick revision note for class-8 Mathematics, Chemistry, Math’s, Biology and other subject are very helpful to revise the whole syllabus during exam days. The revision notes covers all important formulas and concepts given in the chapter. Even if you wish to have an overview of a chapter, quick revision notes are here to do if for you. These notes will certainly save your time during stressful exam days.

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