NCERT Solutions for Class 9 Maths Chapter 7: Triangles

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The NCERT Solutions for class 9 Maths Chapter 7 Triangles are included in the article below. A triangle is a closed shape with three angles, three sides, and three vertices. It has two basic formulas that help us to determine its area and perimeter.

Class 9 Maths Chapter 7 Triangles belong to Unit 4 Geometry which has a weightage of 27 marks in the Class 9 Maths Examination. Class 9 Maths Chapter 7 has the following important concepts: 

Download: NCERT Solutions for Class 9 Mathematics Chapter 7 pdf


NCERT Solutions for Class 9 Mathematics Chapter 7

The Chapter 7 Class 9 Maths are given below:

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Important Topics in Class 9 Maths Chapter 7 Triangles

Important Topics in Class 9 Maths Chapter 7 Triangles are elaborated below:

Area of Triangles

The area of a triangle is the space confined within the three sides of a triangle. For calculating its area, the base length and the height of the triangle are required.

Example: What is the formula to determine the area of a triangle?

Solution: The formula to determine the Area of a Triangle is:
Area of triangle = ½ (base x height) = ½ b x h

Perimeter of Triangles

The perimeter of a respective triangle can be defined as the sum of three sides of the triangle. For example, if a triangle has sides ABC, then the perimeter of it would be (AB + BC + AC).

  1. Perimeter of Scalene Triangle:  A + B + C
  2. Perimeter of Iosceles Triangle: 2A + B
  3. Perimeter of Equilateral Triangle: 3A

Congruency of Triangles

If two triangles have the same shape and size, then they are found congruent to one another.

Example: List all the followed criteria for congruency in a triangle.

Solution: The criteria of conguency in Triangles are: 

  • SSS (side-side-side) congruency
  • SAS (side-angle-side) congruency
  • ASA (angle-side-angle) congruency
  • AAS (angle-angle-side) congruency
  • RHS (right angle-hypotenuse-side) congruency

NCERT Solutions for Class 9 Maths Chapter 7 Exercises:

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

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CBSE X Related Questions

  • 1.
    In a class test, the sum of Anamika's marks obtained in Maths and Science is 30. Had she got 2 marks more in Maths and 3 marks less in Science, the product of the marks would have been 210. Find the marks she got in the two subjects.


      • 2.
        If \(PQ\) and \(PR\) are tangents to the circle with centre \(O\) and radius \(4 \text{ cm}\) such that \(\angle QPR = 90^{\circ}\), then the length \(OP\) is

          • \(4 \text{ cm}\)
          • \(4\sqrt{2} \text{ cm}\)
          • \(8 \text{ cm}\)
          • \(2\sqrt{2} \text{ cm}\)

        • 3.
          D is the mid-point of side BC of \(\triangle ABC\). CE and BF intersect at O, a point on AD. AD is produced to G such that \(OD = DG\). Prove that OBGC is a parallelogram.


            • 4.
              PQ and PR are two tangents to a circle with centre O and radius 5 cm. AB is another tangent to the circle at C which lies on OP. If \(OP = 13\) cm, then find the length AB and PA.


                • 5.
                  The HCF of 960 and 432 is :

                    • 48
                    • 54
                    • 72
                    • 36

                  • 6.
                    A circle centered at (2, 1) passes through the points A(5, 6) and B(-3, K). Find the value(s) of K. Hence find length of chord AB.

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