Lily designed a deck in her backyard that is in the shape of a quadrilateral that has only 1 pair of parallel sides. What is the shape of the deck?

http://www.mathsisfun.com/quadrilaterals.html

To determine the shape of Lily's deck, we can start by analyzing the given condition: a quadrilateral with only 1 pair of parallel sides.

There are several types of quadrilaterals, but the one that matches this description is called a trapezoid. A trapezoid is a quadrilateral with one pair of parallel sides.

Therefore, the shape of the deck in Lily's backyard is a trapezoid.