A triangle can be named two different ways, and the standard asks for both. These free printable worksheets let you pick which naming a sheet drills — or mix them, so a child has to notice which question they were handed.
If they get stuck
The answer key prints on a separate page.
Naming by angles asks whether the widest corner is acute, right, or obtuse. Naming by sides asks how many of the three lengths match. They are independent: a right triangle can be isosceles, and an obtuse one can be scalene, and children who have only met one naming often assume the two are the same question in different words.
The side-length sheets print all three numbers and draw the triangle to match them, so an isosceles triangle genuinely has two equal sides on the page. A figure that says 8, 8, 5 while looking scalene teaches a child to distrust the picture, which is the last thing a geometry sheet should do.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Classifying triangles, step by step