In Class Presentation
Recommended Age: 4 years and onwards
Purpose: To show the child that equilateral triangles can be subdivided into other types of triangles and preparation for later work in geometry.
Level of Parent Involvement: Medium during the initial presentation then low once the child has been shown and can work independently. The adult must also make the materials prior to the presentation.
Prerequisites
- The child should have worked with the first and second sets of constructive triangles and be able to name the shapes formed by the triangles
Materials
- Set 3 (triangular box) print from PDF
- Scissors
- Laminator
- Laminating sheets
- Small tray or box to keep the constructive triangles
Preparation
- Print set 3 (triangular box) from PDF
- Cut out triangles
- Laminate triangles then trim around the plastic laminating sheet
- Place the triangles in the tray/basket
Steps
- Invite the child letting them know that today you are going to show them the third constructive triangle exercise
- Go with the child to their table
- Take out all pieces from the tray/basket and place on the mat, the child may help
- Invite the child to place the same coloured pieces on top of each other
- Point out the grey triangle saying to the child “I wonder if we can make this same triangle with our other triangles?”
- Take the 2 green right angled scalene triangles, positioning them so their black lines are facing
- Slide together making all black lines touch, forming an equilateral triangle
- Take the 3 yellow obtuse angled isosceles triangles, positioning them so their black lines are facing
- Slide together making all black lines touch forming an equilateral triangle
- Take the 4 small red equilateral triangles, positioning them so their black lines are facing
- Slide together making all black lines touch forming an equilateral triangle
- Say to the child “let’s check to see if we have made the same triangle” (referring to the large grey equilateral triangle)
- Place the grey equilateral triangle on top of the other triangles, showing the child they are the same size
- Mix all the shapes
- Invite the child to have a turn, leaving the child to work independently
- When the child is finished let them know to place the 3rd set next to the 2nd and tell the child they may now explore the 3 sets they have been shown together
Variations
- The child may now use this set of triangles with the first and second set
- You may give the child the language of the parts of the triangle:
- Side, angle, base, vertex (relates to the grey triangle)
- Altitude/height (relates to the black lines on the joined green triangles)
- Centre, angle bisector (relates to the black lines on the joined yellow triangles)
- Midpoint of the side (relates to the joined red triangles)
- The child may trace around the triangle cards and label the parts
