Question Video: Identifying Scalene Triangles Mathematics • 3rd Grade

Video Transcript

How many scalene triangles are there?

In this question, we’re shown some different triangles. And we’re asked to count how many scalene triangles there are. A scalene triangle is a triangle which doesn’t have any equal sides. In other words, all three sides have different lengths. Let’s look more closely at the triangles we’re given. Let’s start with this triangle. We can see that two of its sides are equal in length. They both measure four centimeters. And the other side measures two. This is an isosceles triangle. So, we don’t need to count this one. We’re just looking for scalene triangles.

How about this triangle? One of its sides measures four centimeters, another measures one centimeter, and the third measures three centimeters. All of the sides of this triangle are different lengths. So far, we found one scalene triangle. Let’s look at this triangle now. Its first side measures four centimeters, this side measures two centimeters, and this side measures five centimeters. All of its sides are different lengths. So, this is also a scalene triangle. Now, we found two.

Let’s look more closely at this triangle. We can see that two of its sides are equal in length. One side or the base is five centimeters in length, and the other two measure three centimeters. This is an isosceles triangle. And this triangle is also an isosceles triangle. Two of its sides are equal in length. One of the sides measures three centimeters, and two of the sides measure four centimeters.

We looked closely at the lengths of the sides of each of these triangles. We know that scalene triangles have sides which are all different lengths. We counted the number of scalene triangles. There are two.