NCERT Exemplar Solutions
Class 6 - Mathematics - Unit 9: Symmetry and Practical Geometry - Fill in the Blanks

Question 29

Let’s understand the idea first: A line of symmetry is a line that divides a shape so that the two parts match exactly when folded over that line.

1. Look at some common digits and count their mirror lines.

• 0 → Has two mirror lines (one vertical and one horizontal). So it’s not the answer.
• 8 → Also has two mirror lines (vertical and horizontal). So it’s not the answer.
• 2, 5, 7 → Typically have no mirror line in standard print. So they’re not the answer.

2. Now check the digit 3 carefully.

Draw (or imagine) a horizontal line through the middle of 3.

( ext{Mirror line} ;=; ext{a line that splits a figure into two matching halves} )
( ext{Try a horizontal line across the middle of } 3. )

What happens?
( ext{Top half of } 3 ;longleftrightarrow; ext{Bottom half of } 3 ; ext{(they match)} )

But with a vertical line:
( ext{Left side of } 3 ; otcong; ext{Right side of } 3 ; ext{(they don’t match)} )

3. Conclusion

( ext{Number of mirror lines for } 3 = 1 ) (only the horizontal one).

Answer: 3 has exactly one line of symmetry (a horizontal line) in standard print form.