NCERT Exemplar Solutions
Class 6 - Mathematics - Unit 9: Symmetry and Practical Geometry - True or False Questions
Question 47

Question. 47

If a rectangle has more than two lines of symmetry, then it must be a square.

Answer:

true

Detailed Answer with Explanation:

47. If a rectangle has more than two lines of symmetry, then it must be a square.

Answer: True

Beginner-friendly Explanation (step by step)

Step 1: A line of symmetry is a line that cuts a shape into two matching halves (mirror images).

Step 2: In any rectangle, opposite sides are equal and all angles are right angles.

Step 3: Every rectangle has exactly two “middle” symmetry lines:

  • One vertical line through the centre (splits left–right).
  • One horizontal line through the centre (splits top–bottom).

Step 4: What about the diagonals?

For a general rectangle, the two diagonals are not lines of symmetry because they would try to swap the long side with the short side.

( ext{Let length} = l )

( ext{Let breadth} = b )

( ext{In a general rectangle: } l e b )

If a diagonal were a symmetry line, swapping across it would require the two adjacent sides to match exactly.

( ext{For diagonal symmetry we need } l = b )

Step 5: The condition ( l = b ) means all sides are equal — that turns the rectangle into a square.

( l = b Rightarrow ext{rectangle with equal sides} Rightarrow ext{square} )

Step 6 (Conclusion): A rectangle already has 2 symmetry lines. If it has more than two, the extra ones are the diagonals — and that happens only when ( l = b ), i.e., the rectangle is a square. Therefore, the statement is true.

Quick check: A square has 4 lines of symmetry — vertical, horizontal, and the two diagonals.

NCERT Exemplar Solutions Class 6 – Mathematics – Unit 9: Symmetry and Practical Geometry – True or False Questions | Detailed Answers