Triangle and Rectangle Area on the Coordinate Plane

Begin with Plot Points on the Coordinate Plane so students can read ordered pairs. Then use the reflection and distance pages before the perimeter and area pages, which all rely on finding side lengths from coordinates.

Find the base, height and area of a rectangle and 3 triangles from their vertex coordinates. The height of a triangle is the straight up or down distance from its third vertex to the line through its base. The directions on the page read: Use the coordinates to find the base b and the height h of each figure in units. Then find its area. An answer key is included.

Yes, both. We made it for 6th Grade geometry, and the page works the same whether it lands on a kitchen table or a center rotation. At home, most families go through it together and talk the answers out loud, and that talking is where most of the learning happens with coordinate plane. In class it runs well as independent work while you pull a small group. Print one copy or thirty, whichever the day needs.

Start at the origin, move 4 units left because x is −4, then 2 units up because y is 2. The point lands in Quadrant II.

The x coordinate stays the same and the y coordinate changes sign. (3, 5) reflected across the x axis is (3, −5), and across the y axis it is (−3, 5).

For a horizontal or vertical side, count the units or subtract the coordinates. In rectangle ABCD with A(−4, 3) and B(5, 3), side AB is 9 units long. When a side crosses an axis, add the distances, so (−3, 1) to (4, 1) is 3 + 4 = 7 units.

Use a horizontal side as the base and the vertical distance from the third vertex as the height. Triangle JKL with J(−5, −2), K(5, −2) and L(1, 3) has a base of 10 units and a height of 5 units, so its area is 25 square units.