A triangle has three sides, and their lengths tell us its name. This 3rd grade classifying triangles by side lengths worksheet gives your child six triangles to sort, labelled a to f. Each side carries a number and a unit, such as 4 mm, 5 cm, 7 ft or 4 yd. When all three sides are equal, the triangle is equilateral. When only two sides match, it is an isosceles triangle. If no sides match, the triangle is scalene. Your child reads the three numbers, compares them and then writes the right word under the drawing. The units change from one triangle to the next, so the page also gives practice in reading measures. Page two is the answer key, and it explains each answer in two short lines.