Once the different ways of naming a triangle have been discussed, give children the table ( word, pdf) and ask them to work in pairs to draw at least one triangle in each box. Challenging pupils to draw a picture of a triangle with two right angles or obtuse angles will help them grasp this concept.) Discuss the choice of names - why does an acute triangle need to have three acuteĪngles, but an obtuse triangle only needs one obtuse angle? (Pupils should be encouraged to reason that at least two angles of a triangle always have to be acute, so we are only interested in what the third type of angle is. At this point in the lesson, pupils could be asked to draw some different examples of acuse, obtuse and right triangles and to explore whether or not a triangle can fall into more than one of these categories.

Recap on different types of angles and ask children what they think 'acute' and 'obtuse' triangles are. How many types of triangle do children think there are? Can any triangle be more than one of these types? (Children might notice that right-angled triangles can be either isosceles or scalene.) Go through the different ideas under the 'show' buttons and give pupils the opportunity to support or challenge these ideas, giving Discussing the characteristics of the triangles with others will improve pupils' shape vocabulary as there becomes a need to communicate efficiently.īegin by discussing what pupils already know about naming triangles. The different names a triangle can have and to explore when these definitions can overlap. We should be aiming for learners to be comfortable with Children are often taught about four types of triangles (equilateral, isosceles, scalene and right-angled) in isolation from each other and they may be curious to learn that this is not the whole story. This activity provides an engaging context for children to deepen their understanding of the ways of naming different types of triangles. Look at each space on the grid and try to sketch some different triangles to go in the box.Ĭan you sketch a triangle for every box in the grid? Why/why not? For example, the box at the top on the left is for equilateral acute triangles - these are acute triangles with all three sides the same length. This grid is for matching up the different names for a triangle. How could we do this? What do you think an 'acute triangle' or an 'obtuse triangle' might look like? We normally name triangles by thinking about the lengths of the sides, but in this activity we will also be naming triangles using their angles. Which of these children do you agree with? Why?

Using the angles, you get right-angled, acute or obtuse triangles.' Using the sides, you can have equilateral, isosceles and scalene triangles. 'You can name a triangle using either the sides or the angles of the triangle.

Isosceles scalene right triangle