Parallelograms are squares is sometimes true. Squares are parallelograms is always true. Rhomboids are parallelograms is also always true. So not all parallelograms are squares but some are.
Some parallelograms are squares - the ones which are equiangular (have equal angles) and are equilateral (have equal side lengths). All squares are parallelograms, but only some parallelograms are squares.
why
sometimes
-- A parallelogram is always a quadrilateral. -- A quadrilateral is sometimes a parallelogram.
Yes
It is sometimes true that two parallelograms are similar. The could be congruent, or dissimilar in that one is not an enlargement of the other.
Sometimes * * * * * Never. A parallelogram has two pairs of equal angles opposite one another. A trapezoid does not.
No. Parallelograms are never trapezoids. Trapezoids are never parallelograms.
no
The moon.
The moon.