Consider the following statements:
- Every square is a rectangle.
- Every rectangle is a parallelogram.
- Every parallelogram is not necessarily a square.
Which one of the following conclusions can be drawn on the basis of the above statements ?
All parallelograms are either squares or rectangles.
A non-parallelogram figures cannot be either a square or a rectangle.
All rectangles are either squares or parallelograms.
Squares and rectangles are the only parallelograms.
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC CAPF – 2009
The correct option is B) A non-parallelogram figures cannot be either a square or a rectangle.
Let the statements be:
1. Every square is a rectangle. (Square -> Rectangle)
2. Every rectangle is a parallelogram. (Rectangle -> Parallelogram)
3. Every parallelogram is not necessarily a square. (Parallelogram -/> Square)
From statement 1 and 2, we can form a chain: Square -> Rectangle -> Parallelogram.
This implies that every square is a parallelogram.
Now let’s analyze the conclusions:
A) All parallelograms are either squares or rectangles. This is false. A rhombus is a parallelogram but is not necessarily a square or a rectangle.
B) A non-parallelogram figures cannot be either a square or a rectangle. This is true.
From Rectangle -> Parallelogram, the contrapositive is (Not Parallelogram) -> (Not Rectangle).
From Square -> Rectangle, the contrapositive is (Not Rectangle) -> (Not Square).
Combining these, if a figure is not a parallelogram, then it is not a rectangle. If it is not a rectangle, then it is not a square. Therefore, if a figure is a non-parallelogram, it cannot be a rectangle, and thus cannot be a square. This conclusion is logically derived from the first two statements.
C) All rectangles are either squares or parallelograms. This statement is technically true because all rectangles *are* parallelograms (Statement 2), and the set of squares is a subset of rectangles. So, a rectangle is always in the set of parallelograms, and sometimes in the set of squares. However, the wording “either…or” often implies mutual exclusion or at least that being a parallelogram is not always the case for a rectangle, which contradicts statement 2. Conclusion B is a more direct and stronger inference from the combined statements.
D) Squares and rectangles are the only parallelograms. This is false. Rhombuses and other non-rectangular parallelograms exist.
Conclusion B is the only valid and direct conclusion that can be drawn based on the transitive property implied by the statements.