Which of the following statements is not true ?

Question

Accepted Answer

Option 4 is the correct answer because it states that a quadrilateral with two right angles is known as a trapezium, which is not true. A trapezium (or trapezoid in American English) is defined as a quadrilateral with at least one pair of parallel sides, and there is no requirement regarding the number of right angles. Therefore, the statement in Option 4 is incorrect.

Now, let's explain why each of the other options is correct:

1. **Option 1**: A quadrilateral, in which opposite sides are parallel, is known as a parallelogram.  
   - This statement is true. A parallelogram is defined as a quadrilateral with both pairs of opposite sides parallel. This is a fundamental property of parallelograms.

2. **Option 2**: A quadrilateral, in which all sides but not all the angles are equal, is known as Rhombus.  
   - This statement is true. A rhombus is a type of quadrilateral where all four sides are of equal length, but the angles are not necessarily 90 degrees. The defining feature of a rhombus is the equality of its sides, not its angles.

3. **Option 3**: A quadrilateral, in which opposite sides are equal and all angles are right angles, is known as Rectangle.  
   - This statement is true. A rectangle is defined as a quadrilateral with opposite sides equal and all angles equal to 90 degrees. This is a standard definition of a rectangle.

In summary, Option 4 is the only statement that is not true according to the definitions of these geometric shapes, which is why it is the correct answer.