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PROPORTIONS

Direct and inverse proportions of Class 8

The equality of ratios is called “proportion”. 

If a : b :: c : d then a, b, c and d are said to be in proportion. Then a, b, c and d are called terms. 

The first and fourth i.e. a and d are called extremas and second and third term i.e. a and d are called mean terms and d is called the fourth proportional. 

If four quantities be in proportion, the product of the extremas is equal to the product of the means. 

Proportional relationships tell us that two variables scale with each other in a predictable way:

If you drive twice as fast, you'll go twice as far in a given time: Speed and distance are directly proportional to each other.

If you drive twice as fast, it takes half the time to go a set distance: Speed and time are inversely proportional to each other.

To show proportionality we use a Greek alpha symbol in place of an =.

Sometimes we use a constant k to show that need to either multiply or divide something by our other variable.

DIRECT PROPORTIONALITY OR DIRECT VARIATION:

If two quantities are linked in such a way that an increase in one quantity lead to a corresponding increase in the other and vice−versa, then such a variation is called direct variation. 

If two things are directly proportional to each other, they will increase and decrease in the same proportion to each other - double one, double the other; increase one by 12%, the other increases by 12%.

We can find the exact link by looking at the numbers: If we know that the cost of a taxi journey is directly proportional to the distance travelled - which it probably isn't, but let's press on - we can use any pair of values to find the relationship between cost and distance:

If a 300 mile journey cost £1200, we could work out that a 30 mile taxi ride would cost £120, and a 3 mile journey would be £12 - meaning that the trip costs £4 a mile. We could then find the cost of any distance travelled, or how far we could get for a given price.

In this example, our constant k = 4, as the cost = 4 x the distance in miles.

CBSE NCERT Solutions for Class 8 Maths

class 8 maths NCERT solutions Chapter 1: Rational Numbers

class 8 maths NCERT solutions  Chapter 2: Linear Equations in One Variable

class 8 maths NCERT solutions  Chapter 3: Understanding Quadrilaterals

class 8 maths NCERT solutions Chapter 4: Practical Geometry

class 8 maths NCERT solutions  Chapter 5: Data Handling

class 8 maths NCERT solutions  Chapter 6: Square and Square Roots

class 8 maths NCERT solutions  Chapter 7: Cube and Cube Roots

class 8 maths NCERT solutions  Chapter 8: Comparing Quantities

NCERT Class 8 Maths solution Chapter 9: Algebraic Expressions and Identities

class 8 maths NCERT solutions  Chapter 10: Visualizing Solid Shapes

class 8 maths NCERT solutions Chapter 11: Mensuration

class 8 maths NCERT solutions  Chapter 12: Exponents and Powers

class 8 maths NCERT solutions  Chapter 13: Direct and Inverse Proportions

class 8 maths NCERT solutions  Chapter 14: Factorization

class 8 maths NCERT solutions  Chapter 15: Introduction to Graphs

class 8 maths NCERT solutions  Chapter 16: Playing with Numbers

 

Notes,worksheet and solved question for Maths class 8 

  1.  class 8 maths notes on chapter Liner equation in one variable
  2. class 8 maths notes on chapter algebric expression 
  3. class 8 maths notes on chapter Mensuration 
  4. class 8 maths notes on chapter Square and square roots 
  5. class 8 maths notes on chapter statistice
  6. class 8 maths notes on chapter practical Geometry
  7. class 8 maths notes on chapter commericial maths
  8. class 8 maths notes on chapter solid shape
  9. class 8 maths notes on chapter quadrilaterals
  10. class 8 maths notes on chapter exponents
  11. class 8 maths notes on chapter factorisation 
  12. class 8 maths notes on chapter inverse proporation 
  13. class 8 maths notes on chapter cube and cube roots 

Check your marks in a chapter which you have complited in school from Physics Wallah chapter wise online test just click on the link given below

chapter wise online test for class 8 maths 

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