NCERT Exemplar Solutions
Class 6 - Mathematics - Unit 2: Geometry - Fill in the Blanks
Question 23

Question. 23

The number of triangles in Fig. 2.17 is _____. Their names are __________________.

Answer:

Number of triangles = 8. Names: △AOB, △BOC, △COD, △DOA, △ABC, △BCD, △CDA, △DAB.

Detailed Answer with Explanation:

Step-by-step counting

  1. Note: The diagonals AC and BD intersect at point O.
  2. Small triangles around O (formed by the diagonals):
    • △AOB
    • △BOC
    • △COD
    • △DOA

    Count so far = 4.

  3. Big triangles using the sides of ABCD (each uses one diagonal as a side):
    • △ABC
    • △BCD
    • △CDA
    • △DAB

    More triangles = 4.

  4. No double counting: Every triangle listed has different three vertices.
  5. Total triangles = 4 (small) + 4 (big) = 8.
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