Question:medium

Find the number of triangles in the given figure.

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For these patterns, memorize the sequence: 1 level = 1; 2 levels = 5; 3 levels = 13; 4 levels = 27; 5 levels = 48. It saves immense time during competitive exams!
Updated On: Apr 18, 2026
  • 18
  • 20
  • 24
  • 27
  • 30
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The Correct Option is D

Solution and Explanation

Step 1: Understanding the Question:
We need to find the total number of triangles of all sizes in the given complex geometric figure.
Step 2: Key Formula or Approach:
A systematic counting method is essential to avoid missing triangles or counting them more than once. We will break down the figure into distinct regions or types of triangles and sum the counts. We can categorize the triangles into three groups:
1. Triangles belonging to the inner square and its diagonals.
2. Triangles belonging to the outer square and its diagonals.
3. Triangles that connect the inner and outer squares.
Step 3: Detailed Explanation:
Part 1: Triangles in the Inner Square Structure
The inner square and its diagonals form a standard pattern.
- There are 4 small triangles with a vertex at the center (O).
- There are 4 larger triangles formed by combining two adjacent small triangles.
- Total from the inner structure = 4 + 4 = 8 triangles.
Part 2: Triangles in the Outer Square Structure
Similarly, the outer square and its diagonals form the same pattern.
- There are 4 triangles with a vertex at the center (O).
- There are 4 large triangles that are halves of the square.
- Total from the outer structure = 4 + 4 = 8 triangles.
Part 3: Triangles Connecting the Inner and Outer Squares
These triangles have vertices on both the inner and outer squares. They are formed by the sides of the squares and the lines connecting their corresponding vertices.
- At the top, we have triangles AEF and BEF.
- On the right, we have triangles BFG and CFG.
- At the bottom, we have triangles CGH and DGH.
- On the left, we have triangles DHE and AHE.
- This gives a total of 2 + 2 + 2 + 2 = 8 triangles.
Summing the Counts:
To get the total number of triangles, we add the counts from the three distinct categories.
\[ \text{Total} = (\text{Inner triangles}) + (\text{Outer triangles}) + (\text{Connecting triangles}) \] \[ \text{Total} = 8 + 8 + 8 = 24 \] This method accounts for all triangles without any overlap.
Step 4: Final Answer:
The total number of triangles in the given figure is 24.
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