A parallelogram is a figure of four sides, such that opposite sides are parallel
A rectangle is a four-sided figure such that all internal angles are 90°
Here, the statement is:
"A rectangle is sometimes a parallelogram but a parallelogram is always a
rectangle."
Here if we found a parallelogram that is not a rectangle, then that is enough to prove that the statement is false.
The counterexample is a rhombus, which is a parallelogram that has two internal angles smaller than 90° and two internal angles larger than 90°, then this parallelogram is not a rectangle, then the statement is false.
The correct statement would be:
"A parallelogram is sometimes a rectangle, but a rectangle is always a parallelogram"
