The least number of squares to be added in the figure to make AB a line of
symmetry is
Options:
(A) 6
(B) 4
(C) 5
(D) 7
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2024 Q.10)**
**1. Governing Concept**:
- **Topic**: Spatial Aptitude & Reflectional Symmetry
- For line AB to be an axis of reflective symmetry, every unit square on one side of line AB must have an exact mirrored counterpart on the opposite side.
- Counting the asymmetrical squares across line AB demonstrates that exactly 6 squares must be added to achieve complete bilateral reflection.
**2. Option Analysis**:
- **Option (A) [6] is CORRECT**: Verified by counting non-symmetric grid units across axis AB.
- **Option (B) [4] is INCORRECT**: Incomplete symmetry restoration.
- **Option (C) [5] is INCORRECT**: Leaves one cell unmirrored.
- **Option (D) [7] is INCORRECT**: Redundant addition.
**3. Final Answer**:
- **Correct Choice**: **A**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.