After the Mathletes became experts at plotting coordinate points in either 1 or 4 quadrants, I created a game that would allow them to plot three points to create a triangle and then classify it as either acute, obtuse, or right and then classify it as either scalene or isosceles. I had them draw the triangle without a ruler deliberately to have them learn to draw straight lines by keeping their focus on the target point as opposed to the pencil. I used an analogy that when you throw a ball you need to focus your eye on the target as opposed to the ball. A 5th grade student of mine at Sage pointed out something to me this week that I have never noticed but is actually the best way to classify triangles as acute, obtuse, or right: simply identify the largest angle of the triangle and name the triangle for that angle. This is so logical and an easy rule to follow. 


With the 3-5th graders I was able to show the children that right angles have slopes that are opposite reciprocals. Also, if two sides of a triangle are equal in length, the right triangle formed by this side will have the same two legs.



1. K-2nd graders will be working with the first quadrant game boards. These are only positive “x” values and only positive “y” values. Look for 1Q in the pdf.

2. 3-5th graders will be working with four quadrant game boards. These are positive or negative “x” values and positive or negative “y” values. Look for 4Q in the pdf.



1. Roll 2 dice, one at a time; the first die is the "x" value, and the second die is the "y" value (for 3-5th graders, flip a coin for each die—heads is positive and tails is negative).

2. Record three sets of coordinates under the graph.

3. Plot each of these three points and connect them to form a triangle.

4. If your three points do not form a triangle, state “None” in the triangle classification and you still get full credit if you are correct that it does not forma  triangle.


Triangle Definitions:

Triangle: polygon formed by three non-collinear points.

Acute: all 3 angles are between 0 and 90 degrees.

Obtuse: 1 angle is between 90 and 180 degrees.

Right: 1 angle is exactly 90 degrees.

Isosceles: at least 2 sides and angles are of equal length.

Scalene: all 3 sides and angles are different.

Not a Triangle: 3 Colinear Points do not form a triangle.


Scoring (game partner is required to check each other plotted points, classification and total score):

1. One point for each correctly plotted point (3 point max).

2. One point for correctly classifying the triangle as acute, obtuse, or right.

3. One point for correctly classifying the triangle as isosceles or scalene.

4. Two points if the three points do not form a triangle, write "none" in each classification line above.

* Maximum of 5 points per graph.

5. Add all of your points on a game page and that is your total score.

Note A: Maximum of 5 points per graph.

Note B: If you incorrectly plot a point, your triangle classification is based on the triangle you drew on your graph.


FINAL SCORE FOR PAGE (add all four scores): __________



Triangles-Plot_Coordinates_1Q_Classify_Game.pdf2.84 MB
Triangles-Plot_Coordinates_4Q_Classify_Game.pdf5.16 MB