NCERT Solutions for Class 9 Maths Chapter 8 : Quadrilaterals

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The NCERT Solutions for Class 9 Mathematics have been provided in this article. Quadrilaterals include more than one type of shape, but all quadrilaterals have four sides. The most common type of quadrilateral is square, but rectangles and rhombuses are considered quadrilaterals too. Quadrilaterals are also called quadrangles and tetragons. 

Class 9 Maths Chapter 8 Quadrilaterals belong to Unit 4 Geometry which has a weightage of 27 marks in the Class 9 Maths Examination. NCERT Solutions for Class 9 Maths for Chapter 8 cover the following important concepts: 

  1. Cyclic quadrilateral
  2. Quadrilateral angle sum property
  3. Perimeter of a parallelogram

Download: NCERT Solutions for Class 9 Mathematics Chapter 8 pdf


NCERT Solutions for Class 9 Maths Chapter 8


Important Topics in Class 9 Maths Chapter 8 Quadrilaterals

Important Topics in Class 9 Maths Chapter 8 Quadrilaterals are elaborated below:

Cyclic Quadrilateral

Cyclic quadrilateral is a type of quadrilateral which has all of its four vertices lying on the circumference of a circle. Cyclic quadrilteral is a unique four-sided quadrilateral circumscribed in a circle.

Important Points of a Cyclic Quadrilateral:

  • The sides of a cyclic quadrilateral that are found to touch the circumference of a circle are the same four chords of the circle.
  • Area of a cyclic quadrilateral = √(s−a)(s−b)(s−c)(s−d) where a, b, c, and d are the four sides and S is the semi perimeter.
  • Perimeter of a cyclic quadrilateral = 2S, where S = (1/2) × (a + b + c + d) 

Quadrilateral Angle Sum Property

Quadrilateral Angle sum property states that the sum of all four interior angles is equal to 360o. 

Example: Assume that the sum of three interior angles of a quadrilateral is 240o. With the given data, determine its fourth angle. 

Solution: First, consider that the fourth angle is x
Now, since the sum of four interior angles of a quadrilateral is 360o, we can say,
⇒ x + 240o = 360o
⇒ x = 120o

Perimeter of a Paralellogram

The perimeter of a parallelogram can be defined as the sum of the total distance outside its shape. A paralellogram is a four-sided polygon with parallel sides that never intersect.

Perimeter of Paralellogram Formula:
Perimeter of parallelogram =  a + b + c + d
⇒ 2a + 2b= 2(a+b)
⇒ P = 2(a+b).


NCERT Solutions for Class 9 Maths Chapter 8 Exercises:

The detailed solutions for all the NCERT Solutions for Quadrilaterals under different exercises are:

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CBSE X Related Questions

  • 1.
    If for a data, median is 5 and mode is 4, then mean is equal to :

      • 7
      • 11
      • \(\frac{11}{2}\)
      • \(\frac{14}{3}\)

    • 2.
      There are two sections A and B of Grade X. There are 28 students in Section A and 30 students in Section B. What is the minimum number of books you will acquire for the class library so that they can be distributed equally among students of Section A or Section B ?

        • 144
        • 2
        • 420
        • 272

      • 3.
        If the zeroes of the polynomial \(p(x) = 2x^2 - 7x + 6\) are \(\alpha\) and \(\beta\), then the value of \(\frac{1}{\alpha} + \frac{1}{\beta}\) is

          • \(\frac{7}{2}\)
          • \(\frac{6}{7}\)
          • \(\frac{-7}{6}\)
          • \(\frac{7}{6}\)

        • 4.
          If roots of the quadratic equation \(x^2 - k\sqrt{3}x + 2 = 0\) are real and equal, then value of k is

            • \(-2\)
            • \(\sqrt{\frac{8}{3}}\)
            • \(1\)
            • \(2\)

          • 5.
            The graph of a quadratic polynomial f(x) passes through (5,0), (0, -1) and (-2, 0). The two factors of the polynomial are

              • \((x + 2), (x - 5)\)
              • \((x + 5), (x - 2)\)
              • \((x + 1), (x - 5)\)
              • \((x - 1), (x + 2)\)

            • 6.
              If \( \alpha \) and \( \beta \) are two zeroes of a polynomial \( f(x) = px^2 - 2x + 3p \) and \( \alpha + \beta = \alpha\beta \), then value of p is :

                • \( -\frac{2}{3} \)
                • \( \frac{2}{3} \)
                • \( \frac{1}{3} \)
                • \( -\frac{1}{3} \)

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